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TOMOYO Linux Cross Reference
Linux/mm/swapfile.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/mm/swapfile.c
  4  *
  5  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  6  *  Swap reorganised 29.12.95, Stephen Tweedie
  7  */
  8 
  9 #include <linux/mm.h>
 10 #include <linux/sched/mm.h>
 11 #include <linux/sched/task.h>
 12 #include <linux/hugetlb.h>
 13 #include <linux/mman.h>
 14 #include <linux/slab.h>
 15 #include <linux/kernel_stat.h>
 16 #include <linux/swap.h>
 17 #include <linux/vmalloc.h>
 18 #include <linux/pagemap.h>
 19 #include <linux/namei.h>
 20 #include <linux/shmem_fs.h>
 21 #include <linux/blk-cgroup.h>
 22 #include <linux/random.h>
 23 #include <linux/writeback.h>
 24 #include <linux/proc_fs.h>
 25 #include <linux/seq_file.h>
 26 #include <linux/init.h>
 27 #include <linux/ksm.h>
 28 #include <linux/rmap.h>
 29 #include <linux/security.h>
 30 #include <linux/backing-dev.h>
 31 #include <linux/mutex.h>
 32 #include <linux/capability.h>
 33 #include <linux/syscalls.h>
 34 #include <linux/memcontrol.h>
 35 #include <linux/poll.h>
 36 #include <linux/oom.h>
 37 #include <linux/frontswap.h>
 38 #include <linux/swapfile.h>
 39 #include <linux/export.h>
 40 #include <linux/swap_slots.h>
 41 #include <linux/sort.h>
 42 #include <linux/completion.h>
 43 
 44 #include <asm/tlbflush.h>
 45 #include <linux/swapops.h>
 46 #include <linux/swap_cgroup.h>
 47 
 48 static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
 49                                  unsigned char);
 50 static void free_swap_count_continuations(struct swap_info_struct *);
 51 
 52 DEFINE_SPINLOCK(swap_lock);
 53 static unsigned int nr_swapfiles;
 54 atomic_long_t nr_swap_pages;
 55 /*
 56  * Some modules use swappable objects and may try to swap them out under
 57  * memory pressure (via the shrinker). Before doing so, they may wish to
 58  * check to see if any swap space is available.
 59  */
 60 EXPORT_SYMBOL_GPL(nr_swap_pages);
 61 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
 62 long total_swap_pages;
 63 static int least_priority = -1;
 64 
 65 static const char Bad_file[] = "Bad swap file entry ";
 66 static const char Unused_file[] = "Unused swap file entry ";
 67 static const char Bad_offset[] = "Bad swap offset entry ";
 68 static const char Unused_offset[] = "Unused swap offset entry ";
 69 
 70 /*
 71  * all active swap_info_structs
 72  * protected with swap_lock, and ordered by priority.
 73  */
 74 PLIST_HEAD(swap_active_head);
 75 
 76 /*
 77  * all available (active, not full) swap_info_structs
 78  * protected with swap_avail_lock, ordered by priority.
 79  * This is used by get_swap_page() instead of swap_active_head
 80  * because swap_active_head includes all swap_info_structs,
 81  * but get_swap_page() doesn't need to look at full ones.
 82  * This uses its own lock instead of swap_lock because when a
 83  * swap_info_struct changes between not-full/full, it needs to
 84  * add/remove itself to/from this list, but the swap_info_struct->lock
 85  * is held and the locking order requires swap_lock to be taken
 86  * before any swap_info_struct->lock.
 87  */
 88 static struct plist_head *swap_avail_heads;
 89 static DEFINE_SPINLOCK(swap_avail_lock);
 90 
 91 struct swap_info_struct *swap_info[MAX_SWAPFILES];
 92 
 93 static DEFINE_MUTEX(swapon_mutex);
 94 
 95 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
 96 /* Activity counter to indicate that a swapon or swapoff has occurred */
 97 static atomic_t proc_poll_event = ATOMIC_INIT(0);
 98 
 99 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
100 
101 static struct swap_info_struct *swap_type_to_swap_info(int type)
102 {
103         if (type >= MAX_SWAPFILES)
104                 return NULL;
105 
106         return READ_ONCE(swap_info[type]); /* rcu_dereference() */
107 }
108 
109 static inline unsigned char swap_count(unsigned char ent)
110 {
111         return ent & ~SWAP_HAS_CACHE;   /* may include COUNT_CONTINUED flag */
112 }
113 
114 /* Reclaim the swap entry anyway if possible */
115 #define TTRS_ANYWAY             0x1
116 /*
117  * Reclaim the swap entry if there are no more mappings of the
118  * corresponding page
119  */
120 #define TTRS_UNMAPPED           0x2
121 /* Reclaim the swap entry if swap is getting full*/
122 #define TTRS_FULL               0x4
123 
124 /* returns 1 if swap entry is freed */
125 static int __try_to_reclaim_swap(struct swap_info_struct *si,
126                                  unsigned long offset, unsigned long flags)
127 {
128         swp_entry_t entry = swp_entry(si->type, offset);
129         struct page *page;
130         int ret = 0;
131 
132         page = find_get_page(swap_address_space(entry), offset);
133         if (!page)
134                 return 0;
135         /*
136          * When this function is called from scan_swap_map_slots() and it's
137          * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
138          * here. We have to use trylock for avoiding deadlock. This is a special
139          * case and you should use try_to_free_swap() with explicit lock_page()
140          * in usual operations.
141          */
142         if (trylock_page(page)) {
143                 if ((flags & TTRS_ANYWAY) ||
144                     ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
145                     ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
146                         ret = try_to_free_swap(page);
147                 unlock_page(page);
148         }
149         put_page(page);
150         return ret;
151 }
152 
153 static inline struct swap_extent *first_se(struct swap_info_struct *sis)
154 {
155         struct rb_node *rb = rb_first(&sis->swap_extent_root);
156         return rb_entry(rb, struct swap_extent, rb_node);
157 }
158 
159 static inline struct swap_extent *next_se(struct swap_extent *se)
160 {
161         struct rb_node *rb = rb_next(&se->rb_node);
162         return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
163 }
164 
165 /*
166  * swapon tell device that all the old swap contents can be discarded,
167  * to allow the swap device to optimize its wear-levelling.
168  */
169 static int discard_swap(struct swap_info_struct *si)
170 {
171         struct swap_extent *se;
172         sector_t start_block;
173         sector_t nr_blocks;
174         int err = 0;
175 
176         /* Do not discard the swap header page! */
177         se = first_se(si);
178         start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
179         nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
180         if (nr_blocks) {
181                 err = blkdev_issue_discard(si->bdev, start_block,
182                                 nr_blocks, GFP_KERNEL, 0);
183                 if (err)
184                         return err;
185                 cond_resched();
186         }
187 
188         for (se = next_se(se); se; se = next_se(se)) {
189                 start_block = se->start_block << (PAGE_SHIFT - 9);
190                 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
191 
192                 err = blkdev_issue_discard(si->bdev, start_block,
193                                 nr_blocks, GFP_KERNEL, 0);
194                 if (err)
195                         break;
196 
197                 cond_resched();
198         }
199         return err;             /* That will often be -EOPNOTSUPP */
200 }
201 
202 static struct swap_extent *
203 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
204 {
205         struct swap_extent *se;
206         struct rb_node *rb;
207 
208         rb = sis->swap_extent_root.rb_node;
209         while (rb) {
210                 se = rb_entry(rb, struct swap_extent, rb_node);
211                 if (offset < se->start_page)
212                         rb = rb->rb_left;
213                 else if (offset >= se->start_page + se->nr_pages)
214                         rb = rb->rb_right;
215                 else
216                         return se;
217         }
218         /* It *must* be present */
219         BUG();
220 }
221 
222 sector_t swap_page_sector(struct page *page)
223 {
224         struct swap_info_struct *sis = page_swap_info(page);
225         struct swap_extent *se;
226         sector_t sector;
227         pgoff_t offset;
228 
229         offset = __page_file_index(page);
230         se = offset_to_swap_extent(sis, offset);
231         sector = se->start_block + (offset - se->start_page);
232         return sector << (PAGE_SHIFT - 9);
233 }
234 
235 /*
236  * swap allocation tell device that a cluster of swap can now be discarded,
237  * to allow the swap device to optimize its wear-levelling.
238  */
239 static void discard_swap_cluster(struct swap_info_struct *si,
240                                  pgoff_t start_page, pgoff_t nr_pages)
241 {
242         struct swap_extent *se = offset_to_swap_extent(si, start_page);
243 
244         while (nr_pages) {
245                 pgoff_t offset = start_page - se->start_page;
246                 sector_t start_block = se->start_block + offset;
247                 sector_t nr_blocks = se->nr_pages - offset;
248 
249                 if (nr_blocks > nr_pages)
250                         nr_blocks = nr_pages;
251                 start_page += nr_blocks;
252                 nr_pages -= nr_blocks;
253 
254                 start_block <<= PAGE_SHIFT - 9;
255                 nr_blocks <<= PAGE_SHIFT - 9;
256                 if (blkdev_issue_discard(si->bdev, start_block,
257                                         nr_blocks, GFP_NOIO, 0))
258                         break;
259 
260                 se = next_se(se);
261         }
262 }
263 
264 #ifdef CONFIG_THP_SWAP
265 #define SWAPFILE_CLUSTER        HPAGE_PMD_NR
266 
267 #define swap_entry_size(size)   (size)
268 #else
269 #define SWAPFILE_CLUSTER        256
270 
271 /*
272  * Define swap_entry_size() as constant to let compiler to optimize
273  * out some code if !CONFIG_THP_SWAP
274  */
275 #define swap_entry_size(size)   1
276 #endif
277 #define LATENCY_LIMIT           256
278 
279 static inline void cluster_set_flag(struct swap_cluster_info *info,
280         unsigned int flag)
281 {
282         info->flags = flag;
283 }
284 
285 static inline unsigned int cluster_count(struct swap_cluster_info *info)
286 {
287         return info->data;
288 }
289 
290 static inline void cluster_set_count(struct swap_cluster_info *info,
291                                      unsigned int c)
292 {
293         info->data = c;
294 }
295 
296 static inline void cluster_set_count_flag(struct swap_cluster_info *info,
297                                          unsigned int c, unsigned int f)
298 {
299         info->flags = f;
300         info->data = c;
301 }
302 
303 static inline unsigned int cluster_next(struct swap_cluster_info *info)
304 {
305         return info->data;
306 }
307 
308 static inline void cluster_set_next(struct swap_cluster_info *info,
309                                     unsigned int n)
310 {
311         info->data = n;
312 }
313 
314 static inline void cluster_set_next_flag(struct swap_cluster_info *info,
315                                          unsigned int n, unsigned int f)
316 {
317         info->flags = f;
318         info->data = n;
319 }
320 
321 static inline bool cluster_is_free(struct swap_cluster_info *info)
322 {
323         return info->flags & CLUSTER_FLAG_FREE;
324 }
325 
326 static inline bool cluster_is_null(struct swap_cluster_info *info)
327 {
328         return info->flags & CLUSTER_FLAG_NEXT_NULL;
329 }
330 
331 static inline void cluster_set_null(struct swap_cluster_info *info)
332 {
333         info->flags = CLUSTER_FLAG_NEXT_NULL;
334         info->data = 0;
335 }
336 
337 static inline bool cluster_is_huge(struct swap_cluster_info *info)
338 {
339         if (IS_ENABLED(CONFIG_THP_SWAP))
340                 return info->flags & CLUSTER_FLAG_HUGE;
341         return false;
342 }
343 
344 static inline void cluster_clear_huge(struct swap_cluster_info *info)
345 {
346         info->flags &= ~CLUSTER_FLAG_HUGE;
347 }
348 
349 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
350                                                      unsigned long offset)
351 {
352         struct swap_cluster_info *ci;
353 
354         ci = si->cluster_info;
355         if (ci) {
356                 ci += offset / SWAPFILE_CLUSTER;
357                 spin_lock(&ci->lock);
358         }
359         return ci;
360 }
361 
362 static inline void unlock_cluster(struct swap_cluster_info *ci)
363 {
364         if (ci)
365                 spin_unlock(&ci->lock);
366 }
367 
368 /*
369  * Determine the locking method in use for this device.  Return
370  * swap_cluster_info if SSD-style cluster-based locking is in place.
371  */
372 static inline struct swap_cluster_info *lock_cluster_or_swap_info(
373                 struct swap_info_struct *si, unsigned long offset)
374 {
375         struct swap_cluster_info *ci;
376 
377         /* Try to use fine-grained SSD-style locking if available: */
378         ci = lock_cluster(si, offset);
379         /* Otherwise, fall back to traditional, coarse locking: */
380         if (!ci)
381                 spin_lock(&si->lock);
382 
383         return ci;
384 }
385 
386 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
387                                                struct swap_cluster_info *ci)
388 {
389         if (ci)
390                 unlock_cluster(ci);
391         else
392                 spin_unlock(&si->lock);
393 }
394 
395 static inline bool cluster_list_empty(struct swap_cluster_list *list)
396 {
397         return cluster_is_null(&list->head);
398 }
399 
400 static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
401 {
402         return cluster_next(&list->head);
403 }
404 
405 static void cluster_list_init(struct swap_cluster_list *list)
406 {
407         cluster_set_null(&list->head);
408         cluster_set_null(&list->tail);
409 }
410 
411 static void cluster_list_add_tail(struct swap_cluster_list *list,
412                                   struct swap_cluster_info *ci,
413                                   unsigned int idx)
414 {
415         if (cluster_list_empty(list)) {
416                 cluster_set_next_flag(&list->head, idx, 0);
417                 cluster_set_next_flag(&list->tail, idx, 0);
418         } else {
419                 struct swap_cluster_info *ci_tail;
420                 unsigned int tail = cluster_next(&list->tail);
421 
422                 /*
423                  * Nested cluster lock, but both cluster locks are
424                  * only acquired when we held swap_info_struct->lock
425                  */
426                 ci_tail = ci + tail;
427                 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
428                 cluster_set_next(ci_tail, idx);
429                 spin_unlock(&ci_tail->lock);
430                 cluster_set_next_flag(&list->tail, idx, 0);
431         }
432 }
433 
434 static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
435                                            struct swap_cluster_info *ci)
436 {
437         unsigned int idx;
438 
439         idx = cluster_next(&list->head);
440         if (cluster_next(&list->tail) == idx) {
441                 cluster_set_null(&list->head);
442                 cluster_set_null(&list->tail);
443         } else
444                 cluster_set_next_flag(&list->head,
445                                       cluster_next(&ci[idx]), 0);
446 
447         return idx;
448 }
449 
450 /* Add a cluster to discard list and schedule it to do discard */
451 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
452                 unsigned int idx)
453 {
454         /*
455          * If scan_swap_map_slots() can't find a free cluster, it will check
456          * si->swap_map directly. To make sure the discarding cluster isn't
457          * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
458          * It will be cleared after discard
459          */
460         memset(si->swap_map + idx * SWAPFILE_CLUSTER,
461                         SWAP_MAP_BAD, SWAPFILE_CLUSTER);
462 
463         cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
464 
465         schedule_work(&si->discard_work);
466 }
467 
468 static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
469 {
470         struct swap_cluster_info *ci = si->cluster_info;
471 
472         cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
473         cluster_list_add_tail(&si->free_clusters, ci, idx);
474 }
475 
476 /*
477  * Doing discard actually. After a cluster discard is finished, the cluster
478  * will be added to free cluster list. caller should hold si->lock.
479 */
480 static void swap_do_scheduled_discard(struct swap_info_struct *si)
481 {
482         struct swap_cluster_info *info, *ci;
483         unsigned int idx;
484 
485         info = si->cluster_info;
486 
487         while (!cluster_list_empty(&si->discard_clusters)) {
488                 idx = cluster_list_del_first(&si->discard_clusters, info);
489                 spin_unlock(&si->lock);
490 
491                 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
492                                 SWAPFILE_CLUSTER);
493 
494                 spin_lock(&si->lock);
495                 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
496                 __free_cluster(si, idx);
497                 memset(si->swap_map + idx * SWAPFILE_CLUSTER,
498                                 0, SWAPFILE_CLUSTER);
499                 unlock_cluster(ci);
500         }
501 }
502 
503 static void swap_discard_work(struct work_struct *work)
504 {
505         struct swap_info_struct *si;
506 
507         si = container_of(work, struct swap_info_struct, discard_work);
508 
509         spin_lock(&si->lock);
510         swap_do_scheduled_discard(si);
511         spin_unlock(&si->lock);
512 }
513 
514 static void swap_users_ref_free(struct percpu_ref *ref)
515 {
516         struct swap_info_struct *si;
517 
518         si = container_of(ref, struct swap_info_struct, users);
519         complete(&si->comp);
520 }
521 
522 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
523 {
524         struct swap_cluster_info *ci = si->cluster_info;
525 
526         VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
527         cluster_list_del_first(&si->free_clusters, ci);
528         cluster_set_count_flag(ci + idx, 0, 0);
529 }
530 
531 static void free_cluster(struct swap_info_struct *si, unsigned long idx)
532 {
533         struct swap_cluster_info *ci = si->cluster_info + idx;
534 
535         VM_BUG_ON(cluster_count(ci) != 0);
536         /*
537          * If the swap is discardable, prepare discard the cluster
538          * instead of free it immediately. The cluster will be freed
539          * after discard.
540          */
541         if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
542             (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
543                 swap_cluster_schedule_discard(si, idx);
544                 return;
545         }
546 
547         __free_cluster(si, idx);
548 }
549 
550 /*
551  * The cluster corresponding to page_nr will be used. The cluster will be
552  * removed from free cluster list and its usage counter will be increased.
553  */
554 static void inc_cluster_info_page(struct swap_info_struct *p,
555         struct swap_cluster_info *cluster_info, unsigned long page_nr)
556 {
557         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
558 
559         if (!cluster_info)
560                 return;
561         if (cluster_is_free(&cluster_info[idx]))
562                 alloc_cluster(p, idx);
563 
564         VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
565         cluster_set_count(&cluster_info[idx],
566                 cluster_count(&cluster_info[idx]) + 1);
567 }
568 
569 /*
570  * The cluster corresponding to page_nr decreases one usage. If the usage
571  * counter becomes 0, which means no page in the cluster is in using, we can
572  * optionally discard the cluster and add it to free cluster list.
573  */
574 static void dec_cluster_info_page(struct swap_info_struct *p,
575         struct swap_cluster_info *cluster_info, unsigned long page_nr)
576 {
577         unsigned long idx = page_nr / SWAPFILE_CLUSTER;
578 
579         if (!cluster_info)
580                 return;
581 
582         VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
583         cluster_set_count(&cluster_info[idx],
584                 cluster_count(&cluster_info[idx]) - 1);
585 
586         if (cluster_count(&cluster_info[idx]) == 0)
587                 free_cluster(p, idx);
588 }
589 
590 /*
591  * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
592  * cluster list. Avoiding such abuse to avoid list corruption.
593  */
594 static bool
595 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
596         unsigned long offset)
597 {
598         struct percpu_cluster *percpu_cluster;
599         bool conflict;
600 
601         offset /= SWAPFILE_CLUSTER;
602         conflict = !cluster_list_empty(&si->free_clusters) &&
603                 offset != cluster_list_first(&si->free_clusters) &&
604                 cluster_is_free(&si->cluster_info[offset]);
605 
606         if (!conflict)
607                 return false;
608 
609         percpu_cluster = this_cpu_ptr(si->percpu_cluster);
610         cluster_set_null(&percpu_cluster->index);
611         return true;
612 }
613 
614 /*
615  * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
616  * might involve allocating a new cluster for current CPU too.
617  */
618 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
619         unsigned long *offset, unsigned long *scan_base)
620 {
621         struct percpu_cluster *cluster;
622         struct swap_cluster_info *ci;
623         unsigned long tmp, max;
624 
625 new_cluster:
626         cluster = this_cpu_ptr(si->percpu_cluster);
627         if (cluster_is_null(&cluster->index)) {
628                 if (!cluster_list_empty(&si->free_clusters)) {
629                         cluster->index = si->free_clusters.head;
630                         cluster->next = cluster_next(&cluster->index) *
631                                         SWAPFILE_CLUSTER;
632                 } else if (!cluster_list_empty(&si->discard_clusters)) {
633                         /*
634                          * we don't have free cluster but have some clusters in
635                          * discarding, do discard now and reclaim them, then
636                          * reread cluster_next_cpu since we dropped si->lock
637                          */
638                         swap_do_scheduled_discard(si);
639                         *scan_base = this_cpu_read(*si->cluster_next_cpu);
640                         *offset = *scan_base;
641                         goto new_cluster;
642                 } else
643                         return false;
644         }
645 
646         /*
647          * Other CPUs can use our cluster if they can't find a free cluster,
648          * check if there is still free entry in the cluster
649          */
650         tmp = cluster->next;
651         max = min_t(unsigned long, si->max,
652                     (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
653         if (tmp < max) {
654                 ci = lock_cluster(si, tmp);
655                 while (tmp < max) {
656                         if (!si->swap_map[tmp])
657                                 break;
658                         tmp++;
659                 }
660                 unlock_cluster(ci);
661         }
662         if (tmp >= max) {
663                 cluster_set_null(&cluster->index);
664                 goto new_cluster;
665         }
666         cluster->next = tmp + 1;
667         *offset = tmp;
668         *scan_base = tmp;
669         return true;
670 }
671 
672 static void __del_from_avail_list(struct swap_info_struct *p)
673 {
674         int nid;
675 
676         for_each_node(nid)
677                 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
678 }
679 
680 static void del_from_avail_list(struct swap_info_struct *p)
681 {
682         spin_lock(&swap_avail_lock);
683         __del_from_avail_list(p);
684         spin_unlock(&swap_avail_lock);
685 }
686 
687 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
688                              unsigned int nr_entries)
689 {
690         unsigned int end = offset + nr_entries - 1;
691 
692         if (offset == si->lowest_bit)
693                 si->lowest_bit += nr_entries;
694         if (end == si->highest_bit)
695                 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
696         si->inuse_pages += nr_entries;
697         if (si->inuse_pages == si->pages) {
698                 si->lowest_bit = si->max;
699                 si->highest_bit = 0;
700                 del_from_avail_list(si);
701         }
702 }
703 
704 static void add_to_avail_list(struct swap_info_struct *p)
705 {
706         int nid;
707 
708         spin_lock(&swap_avail_lock);
709         for_each_node(nid) {
710                 WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
711                 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
712         }
713         spin_unlock(&swap_avail_lock);
714 }
715 
716 static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
717                             unsigned int nr_entries)
718 {
719         unsigned long begin = offset;
720         unsigned long end = offset + nr_entries - 1;
721         void (*swap_slot_free_notify)(struct block_device *, unsigned long);
722 
723         if (offset < si->lowest_bit)
724                 si->lowest_bit = offset;
725         if (end > si->highest_bit) {
726                 bool was_full = !si->highest_bit;
727 
728                 WRITE_ONCE(si->highest_bit, end);
729                 if (was_full && (si->flags & SWP_WRITEOK))
730                         add_to_avail_list(si);
731         }
732         atomic_long_add(nr_entries, &nr_swap_pages);
733         si->inuse_pages -= nr_entries;
734         if (si->flags & SWP_BLKDEV)
735                 swap_slot_free_notify =
736                         si->bdev->bd_disk->fops->swap_slot_free_notify;
737         else
738                 swap_slot_free_notify = NULL;
739         while (offset <= end) {
740                 arch_swap_invalidate_page(si->type, offset);
741                 frontswap_invalidate_page(si->type, offset);
742                 if (swap_slot_free_notify)
743                         swap_slot_free_notify(si->bdev, offset);
744                 offset++;
745         }
746         clear_shadow_from_swap_cache(si->type, begin, end);
747 }
748 
749 static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
750 {
751         unsigned long prev;
752 
753         if (!(si->flags & SWP_SOLIDSTATE)) {
754                 si->cluster_next = next;
755                 return;
756         }
757 
758         prev = this_cpu_read(*si->cluster_next_cpu);
759         /*
760          * Cross the swap address space size aligned trunk, choose
761          * another trunk randomly to avoid lock contention on swap
762          * address space if possible.
763          */
764         if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
765             (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
766                 /* No free swap slots available */
767                 if (si->highest_bit <= si->lowest_bit)
768                         return;
769                 next = si->lowest_bit +
770                         prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
771                 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
772                 next = max_t(unsigned int, next, si->lowest_bit);
773         }
774         this_cpu_write(*si->cluster_next_cpu, next);
775 }
776 
777 static int scan_swap_map_slots(struct swap_info_struct *si,
778                                unsigned char usage, int nr,
779                                swp_entry_t slots[])
780 {
781         struct swap_cluster_info *ci;
782         unsigned long offset;
783         unsigned long scan_base;
784         unsigned long last_in_cluster = 0;
785         int latency_ration = LATENCY_LIMIT;
786         int n_ret = 0;
787         bool scanned_many = false;
788 
789         /*
790          * We try to cluster swap pages by allocating them sequentially
791          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
792          * way, however, we resort to first-free allocation, starting
793          * a new cluster.  This prevents us from scattering swap pages
794          * all over the entire swap partition, so that we reduce
795          * overall disk seek times between swap pages.  -- sct
796          * But we do now try to find an empty cluster.  -Andrea
797          * And we let swap pages go all over an SSD partition.  Hugh
798          */
799 
800         si->flags += SWP_SCANNING;
801         /*
802          * Use percpu scan base for SSD to reduce lock contention on
803          * cluster and swap cache.  For HDD, sequential access is more
804          * important.
805          */
806         if (si->flags & SWP_SOLIDSTATE)
807                 scan_base = this_cpu_read(*si->cluster_next_cpu);
808         else
809                 scan_base = si->cluster_next;
810         offset = scan_base;
811 
812         /* SSD algorithm */
813         if (si->cluster_info) {
814                 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
815                         goto scan;
816         } else if (unlikely(!si->cluster_nr--)) {
817                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
818                         si->cluster_nr = SWAPFILE_CLUSTER - 1;
819                         goto checks;
820                 }
821 
822                 spin_unlock(&si->lock);
823 
824                 /*
825                  * If seek is expensive, start searching for new cluster from
826                  * start of partition, to minimize the span of allocated swap.
827                  * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
828                  * case, just handled by scan_swap_map_try_ssd_cluster() above.
829                  */
830                 scan_base = offset = si->lowest_bit;
831                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
832 
833                 /* Locate the first empty (unaligned) cluster */
834                 for (; last_in_cluster <= si->highest_bit; offset++) {
835                         if (si->swap_map[offset])
836                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
837                         else if (offset == last_in_cluster) {
838                                 spin_lock(&si->lock);
839                                 offset -= SWAPFILE_CLUSTER - 1;
840                                 si->cluster_next = offset;
841                                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
842                                 goto checks;
843                         }
844                         if (unlikely(--latency_ration < 0)) {
845                                 cond_resched();
846                                 latency_ration = LATENCY_LIMIT;
847                         }
848                 }
849 
850                 offset = scan_base;
851                 spin_lock(&si->lock);
852                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
853         }
854 
855 checks:
856         if (si->cluster_info) {
857                 while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
858                 /* take a break if we already got some slots */
859                         if (n_ret)
860                                 goto done;
861                         if (!scan_swap_map_try_ssd_cluster(si, &offset,
862                                                         &scan_base))
863                                 goto scan;
864                 }
865         }
866         if (!(si->flags & SWP_WRITEOK))
867                 goto no_page;
868         if (!si->highest_bit)
869                 goto no_page;
870         if (offset > si->highest_bit)
871                 scan_base = offset = si->lowest_bit;
872 
873         ci = lock_cluster(si, offset);
874         /* reuse swap entry of cache-only swap if not busy. */
875         if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
876                 int swap_was_freed;
877                 unlock_cluster(ci);
878                 spin_unlock(&si->lock);
879                 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
880                 spin_lock(&si->lock);
881                 /* entry was freed successfully, try to use this again */
882                 if (swap_was_freed)
883                         goto checks;
884                 goto scan; /* check next one */
885         }
886 
887         if (si->swap_map[offset]) {
888                 unlock_cluster(ci);
889                 if (!n_ret)
890                         goto scan;
891                 else
892                         goto done;
893         }
894         WRITE_ONCE(si->swap_map[offset], usage);
895         inc_cluster_info_page(si, si->cluster_info, offset);
896         unlock_cluster(ci);
897 
898         swap_range_alloc(si, offset, 1);
899         slots[n_ret++] = swp_entry(si->type, offset);
900 
901         /* got enough slots or reach max slots? */
902         if ((n_ret == nr) || (offset >= si->highest_bit))
903                 goto done;
904 
905         /* search for next available slot */
906 
907         /* time to take a break? */
908         if (unlikely(--latency_ration < 0)) {
909                 if (n_ret)
910                         goto done;
911                 spin_unlock(&si->lock);
912                 cond_resched();
913                 spin_lock(&si->lock);
914                 latency_ration = LATENCY_LIMIT;
915         }
916 
917         /* try to get more slots in cluster */
918         if (si->cluster_info) {
919                 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
920                         goto checks;
921         } else if (si->cluster_nr && !si->swap_map[++offset]) {
922                 /* non-ssd case, still more slots in cluster? */
923                 --si->cluster_nr;
924                 goto checks;
925         }
926 
927         /*
928          * Even if there's no free clusters available (fragmented),
929          * try to scan a little more quickly with lock held unless we
930          * have scanned too many slots already.
931          */
932         if (!scanned_many) {
933                 unsigned long scan_limit;
934 
935                 if (offset < scan_base)
936                         scan_limit = scan_base;
937                 else
938                         scan_limit = si->highest_bit;
939                 for (; offset <= scan_limit && --latency_ration > 0;
940                      offset++) {
941                         if (!si->swap_map[offset])
942                                 goto checks;
943                 }
944         }
945 
946 done:
947         set_cluster_next(si, offset + 1);
948         si->flags -= SWP_SCANNING;
949         return n_ret;
950 
951 scan:
952         spin_unlock(&si->lock);
953         while (++offset <= READ_ONCE(si->highest_bit)) {
954                 if (data_race(!si->swap_map[offset])) {
955                         spin_lock(&si->lock);
956                         goto checks;
957                 }
958                 if (vm_swap_full() &&
959                     READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
960                         spin_lock(&si->lock);
961                         goto checks;
962                 }
963                 if (unlikely(--latency_ration < 0)) {
964                         cond_resched();
965                         latency_ration = LATENCY_LIMIT;
966                         scanned_many = true;
967                 }
968         }
969         offset = si->lowest_bit;
970         while (offset < scan_base) {
971                 if (data_race(!si->swap_map[offset])) {
972                         spin_lock(&si->lock);
973                         goto checks;
974                 }
975                 if (vm_swap_full() &&
976                     READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
977                         spin_lock(&si->lock);
978                         goto checks;
979                 }
980                 if (unlikely(--latency_ration < 0)) {
981                         cond_resched();
982                         latency_ration = LATENCY_LIMIT;
983                         scanned_many = true;
984                 }
985                 offset++;
986         }
987         spin_lock(&si->lock);
988 
989 no_page:
990         si->flags -= SWP_SCANNING;
991         return n_ret;
992 }
993 
994 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
995 {
996         unsigned long idx;
997         struct swap_cluster_info *ci;
998         unsigned long offset;
999 
1000         /*
1001          * Should not even be attempting cluster allocations when huge
1002          * page swap is disabled.  Warn and fail the allocation.
1003          */
1004         if (!IS_ENABLED(CONFIG_THP_SWAP)) {
1005                 VM_WARN_ON_ONCE(1);
1006                 return 0;
1007         }
1008 
1009         if (cluster_list_empty(&si->free_clusters))
1010                 return 0;
1011 
1012         idx = cluster_list_first(&si->free_clusters);
1013         offset = idx * SWAPFILE_CLUSTER;
1014         ci = lock_cluster(si, offset);
1015         alloc_cluster(si, idx);
1016         cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
1017 
1018         memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
1019         unlock_cluster(ci);
1020         swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
1021         *slot = swp_entry(si->type, offset);
1022 
1023         return 1;
1024 }
1025 
1026 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
1027 {
1028         unsigned long offset = idx * SWAPFILE_CLUSTER;
1029         struct swap_cluster_info *ci;
1030 
1031         ci = lock_cluster(si, offset);
1032         memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
1033         cluster_set_count_flag(ci, 0, 0);
1034         free_cluster(si, idx);
1035         unlock_cluster(ci);
1036         swap_range_free(si, offset, SWAPFILE_CLUSTER);
1037 }
1038 
1039 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
1040 {
1041         unsigned long size = swap_entry_size(entry_size);
1042         struct swap_info_struct *si, *next;
1043         long avail_pgs;
1044         int n_ret = 0;
1045         int node;
1046 
1047         /* Only single cluster request supported */
1048         WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
1049 
1050         spin_lock(&swap_avail_lock);
1051 
1052         avail_pgs = atomic_long_read(&nr_swap_pages) / size;
1053         if (avail_pgs <= 0) {
1054                 spin_unlock(&swap_avail_lock);
1055                 goto noswap;
1056         }
1057 
1058         n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
1059 
1060         atomic_long_sub(n_goal * size, &nr_swap_pages);
1061 
1062 start_over:
1063         node = numa_node_id();
1064         plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
1065                 /* requeue si to after same-priority siblings */
1066                 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
1067                 spin_unlock(&swap_avail_lock);
1068                 spin_lock(&si->lock);
1069                 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
1070                         spin_lock(&swap_avail_lock);
1071                         if (plist_node_empty(&si->avail_lists[node])) {
1072                                 spin_unlock(&si->lock);
1073                                 goto nextsi;
1074                         }
1075                         WARN(!si->highest_bit,
1076                              "swap_info %d in list but !highest_bit\n",
1077                              si->type);
1078                         WARN(!(si->flags & SWP_WRITEOK),
1079                              "swap_info %d in list but !SWP_WRITEOK\n",
1080                              si->type);
1081                         __del_from_avail_list(si);
1082                         spin_unlock(&si->lock);
1083                         goto nextsi;
1084                 }
1085                 if (size == SWAPFILE_CLUSTER) {
1086                         if (si->flags & SWP_BLKDEV)
1087                                 n_ret = swap_alloc_cluster(si, swp_entries);
1088                 } else
1089                         n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
1090                                                     n_goal, swp_entries);
1091                 spin_unlock(&si->lock);
1092                 if (n_ret || size == SWAPFILE_CLUSTER)
1093                         goto check_out;
1094                 pr_debug("scan_swap_map of si %d failed to find offset\n",
1095                         si->type);
1096 
1097                 spin_lock(&swap_avail_lock);
1098 nextsi:
1099                 /*
1100                  * if we got here, it's likely that si was almost full before,
1101                  * and since scan_swap_map_slots() can drop the si->lock,
1102                  * multiple callers probably all tried to get a page from the
1103                  * same si and it filled up before we could get one; or, the si
1104                  * filled up between us dropping swap_avail_lock and taking
1105                  * si->lock. Since we dropped the swap_avail_lock, the
1106                  * swap_avail_head list may have been modified; so if next is
1107                  * still in the swap_avail_head list then try it, otherwise
1108                  * start over if we have not gotten any slots.
1109                  */
1110                 if (plist_node_empty(&next->avail_lists[node]))
1111                         goto start_over;
1112         }
1113 
1114         spin_unlock(&swap_avail_lock);
1115 
1116 check_out:
1117         if (n_ret < n_goal)
1118                 atomic_long_add((long)(n_goal - n_ret) * size,
1119                                 &nr_swap_pages);
1120 noswap:
1121         return n_ret;
1122 }
1123 
1124 static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
1125 {
1126         struct swap_info_struct *p;
1127         unsigned long offset;
1128 
1129         if (!entry.val)
1130                 goto out;
1131         p = swp_swap_info(entry);
1132         if (!p)
1133                 goto bad_nofile;
1134         if (data_race(!(p->flags & SWP_USED)))
1135                 goto bad_device;
1136         offset = swp_offset(entry);
1137         if (offset >= p->max)
1138                 goto bad_offset;
1139         return p;
1140 
1141 bad_offset:
1142         pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
1143         goto out;
1144 bad_device:
1145         pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
1146         goto out;
1147 bad_nofile:
1148         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1149 out:
1150         return NULL;
1151 }
1152 
1153 static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
1154 {
1155         struct swap_info_struct *p;
1156 
1157         p = __swap_info_get(entry);
1158         if (!p)
1159                 goto out;
1160         if (data_race(!p->swap_map[swp_offset(entry)]))
1161                 goto bad_free;
1162         return p;
1163 
1164 bad_free:
1165         pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val);
1166 out:
1167         return NULL;
1168 }
1169 
1170 static struct swap_info_struct *swap_info_get(swp_entry_t entry)
1171 {
1172         struct swap_info_struct *p;
1173 
1174         p = _swap_info_get(entry);
1175         if (p)
1176                 spin_lock(&p->lock);
1177         return p;
1178 }
1179 
1180 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
1181                                         struct swap_info_struct *q)
1182 {
1183         struct swap_info_struct *p;
1184 
1185         p = _swap_info_get(entry);
1186 
1187         if (p != q) {
1188                 if (q != NULL)
1189                         spin_unlock(&q->lock);
1190                 if (p != NULL)
1191                         spin_lock(&p->lock);
1192         }
1193         return p;
1194 }
1195 
1196 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
1197                                               unsigned long offset,
1198                                               unsigned char usage)
1199 {
1200         unsigned char count;
1201         unsigned char has_cache;
1202 
1203         count = p->swap_map[offset];
1204 
1205         has_cache = count & SWAP_HAS_CACHE;
1206         count &= ~SWAP_HAS_CACHE;
1207 
1208         if (usage == SWAP_HAS_CACHE) {
1209                 VM_BUG_ON(!has_cache);
1210                 has_cache = 0;
1211         } else if (count == SWAP_MAP_SHMEM) {
1212                 /*
1213                  * Or we could insist on shmem.c using a special
1214                  * swap_shmem_free() and free_shmem_swap_and_cache()...
1215                  */
1216                 count = 0;
1217         } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
1218                 if (count == COUNT_CONTINUED) {
1219                         if (swap_count_continued(p, offset, count))
1220                                 count = SWAP_MAP_MAX | COUNT_CONTINUED;
1221                         else
1222                                 count = SWAP_MAP_MAX;
1223                 } else
1224                         count--;
1225         }
1226 
1227         usage = count | has_cache;
1228         if (usage)
1229                 WRITE_ONCE(p->swap_map[offset], usage);
1230         else
1231                 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
1232 
1233         return usage;
1234 }
1235 
1236 /*
1237  * Check whether swap entry is valid in the swap device.  If so,
1238  * return pointer to swap_info_struct, and keep the swap entry valid
1239  * via preventing the swap device from being swapoff, until
1240  * put_swap_device() is called.  Otherwise return NULL.
1241  *
1242  * Notice that swapoff or swapoff+swapon can still happen before the
1243  * percpu_ref_tryget_live() in get_swap_device() or after the
1244  * percpu_ref_put() in put_swap_device() if there isn't any other way
1245  * to prevent swapoff, such as page lock, page table lock, etc.  The
1246  * caller must be prepared for that.  For example, the following
1247  * situation is possible.
1248  *
1249  *   CPU1                               CPU2
1250  *   do_swap_page()
1251  *     ...                              swapoff+swapon
1252  *     __read_swap_cache_async()
1253  *       swapcache_prepare()
1254  *         __swap_duplicate()
1255  *           // check swap_map
1256  *     // verify PTE not changed
1257  *
1258  * In __swap_duplicate(), the swap_map need to be checked before
1259  * changing partly because the specified swap entry may be for another
1260  * swap device which has been swapoff.  And in do_swap_page(), after
1261  * the page is read from the swap device, the PTE is verified not
1262  * changed with the page table locked to check whether the swap device
1263  * has been swapoff or swapoff+swapon.
1264  */
1265 struct swap_info_struct *get_swap_device(swp_entry_t entry)
1266 {
1267         struct swap_info_struct *si;
1268         unsigned long offset;
1269 
1270         if (!entry.val)
1271                 goto out;
1272         si = swp_swap_info(entry);
1273         if (!si)
1274                 goto bad_nofile;
1275         if (!percpu_ref_tryget_live(&si->users))
1276                 goto out;
1277         /*
1278          * Guarantee the si->users are checked before accessing other
1279          * fields of swap_info_struct.
1280          *
1281          * Paired with the spin_unlock() after setup_swap_info() in
1282          * enable_swap_info().
1283          */
1284         smp_rmb();
1285         offset = swp_offset(entry);
1286         if (offset >= si->max)
1287                 goto put_out;
1288 
1289         return si;
1290 bad_nofile:
1291         pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
1292 out:
1293         return NULL;
1294 put_out:
1295         percpu_ref_put(&si->users);
1296         return NULL;
1297 }
1298 
1299 static unsigned char __swap_entry_free(struct swap_info_struct *p,
1300                                        swp_entry_t entry)
1301 {
1302         struct swap_cluster_info *ci;
1303         unsigned long offset = swp_offset(entry);
1304         unsigned char usage;
1305 
1306         ci = lock_cluster_or_swap_info(p, offset);
1307         usage = __swap_entry_free_locked(p, offset, 1);
1308         unlock_cluster_or_swap_info(p, ci);
1309         if (!usage)
1310                 free_swap_slot(entry);
1311 
1312         return usage;
1313 }
1314 
1315 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
1316 {
1317         struct swap_cluster_info *ci;
1318         unsigned long offset = swp_offset(entry);
1319         unsigned char count;
1320 
1321         ci = lock_cluster(p, offset);
1322         count = p->swap_map[offset];
1323         VM_BUG_ON(count != SWAP_HAS_CACHE);
1324         p->swap_map[offset] = 0;
1325         dec_cluster_info_page(p, p->cluster_info, offset);
1326         unlock_cluster(ci);
1327 
1328         mem_cgroup_uncharge_swap(entry, 1);
1329         swap_range_free(p, offset, 1);
1330 }
1331 
1332 /*
1333  * Caller has made sure that the swap device corresponding to entry
1334  * is still around or has not been recycled.
1335  */
1336 void swap_free(swp_entry_t entry)
1337 {
1338         struct swap_info_struct *p;
1339 
1340         p = _swap_info_get(entry);
1341         if (p)
1342                 __swap_entry_free(p, entry);
1343 }
1344 
1345 /*
1346  * Called after dropping swapcache to decrease refcnt to swap entries.
1347  */
1348 void put_swap_page(struct page *page, swp_entry_t entry)
1349 {
1350         unsigned long offset = swp_offset(entry);
1351         unsigned long idx = offset / SWAPFILE_CLUSTER;
1352         struct swap_cluster_info *ci;
1353         struct swap_info_struct *si;
1354         unsigned char *map;
1355         unsigned int i, free_entries = 0;
1356         unsigned char val;
1357         int size = swap_entry_size(thp_nr_pages(page));
1358 
1359         si = _swap_info_get(entry);
1360         if (!si)
1361                 return;
1362 
1363         ci = lock_cluster_or_swap_info(si, offset);
1364         if (size == SWAPFILE_CLUSTER) {
1365                 VM_BUG_ON(!cluster_is_huge(ci));
1366                 map = si->swap_map + offset;
1367                 for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1368                         val = map[i];
1369                         VM_BUG_ON(!(val & SWAP_HAS_CACHE));
1370                         if (val == SWAP_HAS_CACHE)
1371                                 free_entries++;
1372                 }
1373                 cluster_clear_huge(ci);
1374                 if (free_entries == SWAPFILE_CLUSTER) {
1375                         unlock_cluster_or_swap_info(si, ci);
1376                         spin_lock(&si->lock);
1377                         mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
1378                         swap_free_cluster(si, idx);
1379                         spin_unlock(&si->lock);
1380                         return;
1381                 }
1382         }
1383         for (i = 0; i < size; i++, entry.val++) {
1384                 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
1385                         unlock_cluster_or_swap_info(si, ci);
1386                         free_swap_slot(entry);
1387                         if (i == size - 1)
1388                                 return;
1389                         lock_cluster_or_swap_info(si, offset);
1390                 }
1391         }
1392         unlock_cluster_or_swap_info(si, ci);
1393 }
1394 
1395 #ifdef CONFIG_THP_SWAP
1396 int split_swap_cluster(swp_entry_t entry)
1397 {
1398         struct swap_info_struct *si;
1399         struct swap_cluster_info *ci;
1400         unsigned long offset = swp_offset(entry);
1401 
1402         si = _swap_info_get(entry);
1403         if (!si)
1404                 return -EBUSY;
1405         ci = lock_cluster(si, offset);
1406         cluster_clear_huge(ci);
1407         unlock_cluster(ci);
1408         return 0;
1409 }
1410 #endif
1411 
1412 static int swp_entry_cmp(const void *ent1, const void *ent2)
1413 {
1414         const swp_entry_t *e1 = ent1, *e2 = ent2;
1415 
1416         return (int)swp_type(*e1) - (int)swp_type(*e2);
1417 }
1418 
1419 void swapcache_free_entries(swp_entry_t *entries, int n)
1420 {
1421         struct swap_info_struct *p, *prev;
1422         int i;
1423 
1424         if (n <= 0)
1425                 return;
1426 
1427         prev = NULL;
1428         p = NULL;
1429 
1430         /*
1431          * Sort swap entries by swap device, so each lock is only taken once.
1432          * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
1433          * so low that it isn't necessary to optimize further.
1434          */
1435         if (nr_swapfiles > 1)
1436                 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
1437         for (i = 0; i < n; ++i) {
1438                 p = swap_info_get_cont(entries[i], prev);
1439                 if (p)
1440                         swap_entry_free(p, entries[i]);
1441                 prev = p;
1442         }
1443         if (p)
1444                 spin_unlock(&p->lock);
1445 }
1446 
1447 /*
1448  * How many references to page are currently swapped out?
1449  * This does not give an exact answer when swap count is continued,
1450  * but does include the high COUNT_CONTINUED flag to allow for that.
1451  */
1452 int page_swapcount(struct page *page)
1453 {
1454         int count = 0;
1455         struct swap_info_struct *p;
1456         struct swap_cluster_info *ci;
1457         swp_entry_t entry;
1458         unsigned long offset;
1459 
1460         entry.val = page_private(page);
1461         p = _swap_info_get(entry);
1462         if (p) {
1463                 offset = swp_offset(entry);
1464                 ci = lock_cluster_or_swap_info(p, offset);
1465                 count = swap_count(p->swap_map[offset]);
1466                 unlock_cluster_or_swap_info(p, ci);
1467         }
1468         return count;
1469 }
1470 
1471 int __swap_count(swp_entry_t entry)
1472 {
1473         struct swap_info_struct *si;
1474         pgoff_t offset = swp_offset(entry);
1475         int count = 0;
1476 
1477         si = get_swap_device(entry);
1478         if (si) {
1479                 count = swap_count(si->swap_map[offset]);
1480                 put_swap_device(si);
1481         }
1482         return count;
1483 }
1484 
1485 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
1486 {
1487         int count = 0;
1488         pgoff_t offset = swp_offset(entry);
1489         struct swap_cluster_info *ci;
1490 
1491         ci = lock_cluster_or_swap_info(si, offset);
1492         count = swap_count(si->swap_map[offset]);
1493         unlock_cluster_or_swap_info(si, ci);
1494         return count;
1495 }
1496 
1497 /*
1498  * How many references to @entry are currently swapped out?
1499  * This does not give an exact answer when swap count is continued,
1500  * but does include the high COUNT_CONTINUED flag to allow for that.
1501  */
1502 int __swp_swapcount(swp_entry_t entry)
1503 {
1504         int count = 0;
1505         struct swap_info_struct *si;
1506 
1507         si = get_swap_device(entry);
1508         if (si) {
1509                 count = swap_swapcount(si, entry);
1510                 put_swap_device(si);
1511         }
1512         return count;
1513 }
1514 
1515 /*
1516  * How many references to @entry are currently swapped out?
1517  * This considers COUNT_CONTINUED so it returns exact answer.
1518  */
1519 int swp_swapcount(swp_entry_t entry)
1520 {
1521         int count, tmp_count, n;
1522         struct swap_info_struct *p;
1523         struct swap_cluster_info *ci;
1524         struct page *page;
1525         pgoff_t offset;
1526         unsigned char *map;
1527 
1528         p = _swap_info_get(entry);
1529         if (!p)
1530                 return 0;
1531 
1532         offset = swp_offset(entry);
1533 
1534         ci = lock_cluster_or_swap_info(p, offset);
1535 
1536         count = swap_count(p->swap_map[offset]);
1537         if (!(count & COUNT_CONTINUED))
1538                 goto out;
1539 
1540         count &= ~COUNT_CONTINUED;
1541         n = SWAP_MAP_MAX + 1;
1542 
1543         page = vmalloc_to_page(p->swap_map + offset);
1544         offset &= ~PAGE_MASK;
1545         VM_BUG_ON(page_private(page) != SWP_CONTINUED);
1546 
1547         do {
1548                 page = list_next_entry(page, lru);
1549                 map = kmap_atomic(page);
1550                 tmp_count = map[offset];
1551                 kunmap_atomic(map);
1552 
1553                 count += (tmp_count & ~COUNT_CONTINUED) * n;
1554                 n *= (SWAP_CONT_MAX + 1);
1555         } while (tmp_count & COUNT_CONTINUED);
1556 out:
1557         unlock_cluster_or_swap_info(p, ci);
1558         return count;
1559 }
1560 
1561 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
1562                                          swp_entry_t entry)
1563 {
1564         struct swap_cluster_info *ci;
1565         unsigned char *map = si->swap_map;
1566         unsigned long roffset = swp_offset(entry);
1567         unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
1568         int i;
1569         bool ret = false;
1570 
1571         ci = lock_cluster_or_swap_info(si, offset);
1572         if (!ci || !cluster_is_huge(ci)) {
1573                 if (swap_count(map[roffset]))
1574                         ret = true;
1575                 goto unlock_out;
1576         }
1577         for (i = 0; i < SWAPFILE_CLUSTER; i++) {
1578                 if (swap_count(map[offset + i])) {
1579                         ret = true;
1580                         break;
1581                 }
1582         }
1583 unlock_out:
1584         unlock_cluster_or_swap_info(si, ci);
1585         return ret;
1586 }
1587 
1588 static bool page_swapped(struct page *page)
1589 {
1590         swp_entry_t entry;
1591         struct swap_info_struct *si;
1592 
1593         if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
1594                 return page_swapcount(page) != 0;
1595 
1596         page = compound_head(page);
1597         entry.val = page_private(page);
1598         si = _swap_info_get(entry);
1599         if (si)
1600                 return swap_page_trans_huge_swapped(si, entry);
1601         return false;
1602 }
1603 
1604 static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
1605                                          int *total_swapcount)
1606 {
1607         int i, map_swapcount, _total_mapcount, _total_swapcount;
1608         unsigned long offset = 0;
1609         struct swap_info_struct *si;
1610         struct swap_cluster_info *ci = NULL;
1611         unsigned char *map = NULL;
1612         int mapcount, swapcount = 0;
1613 
1614         /* hugetlbfs shouldn't call it */
1615         VM_BUG_ON_PAGE(PageHuge(page), page);
1616 
1617         if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
1618                 mapcount = page_trans_huge_mapcount(page, total_mapcount);
1619                 if (PageSwapCache(page))
1620                         swapcount = page_swapcount(page);
1621                 if (total_swapcount)
1622                         *total_swapcount = swapcount;
1623                 return mapcount + swapcount;
1624         }
1625 
1626         page = compound_head(page);
1627 
1628         _total_mapcount = _total_swapcount = map_swapcount = 0;
1629         if (PageSwapCache(page)) {
1630                 swp_entry_t entry;
1631 
1632                 entry.val = page_private(page);
1633                 si = _swap_info_get(entry);
1634                 if (si) {
1635                         map = si->swap_map;
1636                         offset = swp_offset(entry);
1637                 }
1638         }
1639         if (map)
1640                 ci = lock_cluster(si, offset);
1641         for (i = 0; i < HPAGE_PMD_NR; i++) {
1642                 mapcount = atomic_read(&page[i]._mapcount) + 1;
1643                 _total_mapcount += mapcount;
1644                 if (map) {
1645                         swapcount = swap_count(map[offset + i]);
1646                         _total_swapcount += swapcount;
1647                 }
1648                 map_swapcount = max(map_swapcount, mapcount + swapcount);
1649         }
1650         unlock_cluster(ci);
1651         if (PageDoubleMap(page)) {
1652                 map_swapcount -= 1;
1653                 _total_mapcount -= HPAGE_PMD_NR;
1654         }
1655         mapcount = compound_mapcount(page);
1656         map_swapcount += mapcount;
1657         _total_mapcount += mapcount;
1658         if (total_mapcount)
1659                 *total_mapcount = _total_mapcount;
1660         if (total_swapcount)
1661                 *total_swapcount = _total_swapcount;
1662 
1663         return map_swapcount;
1664 }
1665 
1666 /*
1667  * We can write to an anon page without COW if there are no other references
1668  * to it.  And as a side-effect, free up its swap: because the old content
1669  * on disk will never be read, and seeking back there to write new content
1670  * later would only waste time away from clustering.
1671  *
1672  * NOTE: total_map_swapcount should not be relied upon by the caller if
1673  * reuse_swap_page() returns false, but it may be always overwritten
1674  * (see the other implementation for CONFIG_SWAP=n).
1675  */
1676 bool reuse_swap_page(struct page *page, int *total_map_swapcount)
1677 {
1678         int count, total_mapcount, total_swapcount;
1679 
1680         VM_BUG_ON_PAGE(!PageLocked(page), page);
1681         if (unlikely(PageKsm(page)))
1682                 return false;
1683         count = page_trans_huge_map_swapcount(page, &total_mapcount,
1684                                               &total_swapcount);
1685         if (total_map_swapcount)
1686                 *total_map_swapcount = total_mapcount + total_swapcount;
1687         if (count == 1 && PageSwapCache(page) &&
1688             (likely(!PageTransCompound(page)) ||
1689              /* The remaining swap count will be freed soon */
1690              total_swapcount == page_swapcount(page))) {
1691                 if (!PageWriteback(page)) {
1692                         page = compound_head(page);
1693                         delete_from_swap_cache(page);
1694                         SetPageDirty(page);
1695                 } else {
1696                         swp_entry_t entry;
1697                         struct swap_info_struct *p;
1698 
1699                         entry.val = page_private(page);
1700                         p = swap_info_get(entry);
1701                         if (p->flags & SWP_STABLE_WRITES) {
1702                                 spin_unlock(&p->lock);
1703                                 return false;
1704                         }
1705                         spin_unlock(&p->lock);
1706                 }
1707         }
1708 
1709         return count <= 1;
1710 }
1711 
1712 /*
1713  * If swap is getting full, or if there are no more mappings of this page,
1714  * then try_to_free_swap is called to free its swap space.
1715  */
1716 int try_to_free_swap(struct page *page)
1717 {
1718         VM_BUG_ON_PAGE(!PageLocked(page), page);
1719 
1720         if (!PageSwapCache(page))
1721                 return 0;
1722         if (PageWriteback(page))
1723                 return 0;
1724         if (page_swapped(page))
1725                 return 0;
1726 
1727         /*
1728          * Once hibernation has begun to create its image of memory,
1729          * there's a danger that one of the calls to try_to_free_swap()
1730          * - most probably a call from __try_to_reclaim_swap() while
1731          * hibernation is allocating its own swap pages for the image,
1732          * but conceivably even a call from memory reclaim - will free
1733          * the swap from a page which has already been recorded in the
1734          * image as a clean swapcache page, and then reuse its swap for
1735          * another page of the image.  On waking from hibernation, the
1736          * original page might be freed under memory pressure, then
1737          * later read back in from swap, now with the wrong data.
1738          *
1739          * Hibernation suspends storage while it is writing the image
1740          * to disk so check that here.
1741          */
1742         if (pm_suspended_storage())
1743                 return 0;
1744 
1745         page = compound_head(page);
1746         delete_from_swap_cache(page);
1747         SetPageDirty(page);
1748         return 1;
1749 }
1750 
1751 /*
1752  * Free the swap entry like above, but also try to
1753  * free the page cache entry if it is the last user.
1754  */
1755 int free_swap_and_cache(swp_entry_t entry)
1756 {
1757         struct swap_info_struct *p;
1758         unsigned char count;
1759 
1760         if (non_swap_entry(entry))
1761                 return 1;
1762 
1763         p = _swap_info_get(entry);
1764         if (p) {
1765                 count = __swap_entry_free(p, entry);
1766                 if (count == SWAP_HAS_CACHE &&
1767                     !swap_page_trans_huge_swapped(p, entry))
1768                         __try_to_reclaim_swap(p, swp_offset(entry),
1769                                               TTRS_UNMAPPED | TTRS_FULL);
1770         }
1771         return p != NULL;
1772 }
1773 
1774 #ifdef CONFIG_HIBERNATION
1775 
1776 swp_entry_t get_swap_page_of_type(int type)
1777 {
1778         struct swap_info_struct *si = swap_type_to_swap_info(type);
1779         swp_entry_t entry = {0};
1780 
1781         if (!si)
1782                 goto fail;
1783 
1784         /* This is called for allocating swap entry, not cache */
1785         spin_lock(&si->lock);
1786         if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
1787                 atomic_long_dec(&nr_swap_pages);
1788         spin_unlock(&si->lock);
1789 fail:
1790         return entry;
1791 }
1792 
1793 /*
1794  * Find the swap type that corresponds to given device (if any).
1795  *
1796  * @offset - number of the PAGE_SIZE-sized block of the device, starting
1797  * from 0, in which the swap header is expected to be located.
1798  *
1799  * This is needed for the suspend to disk (aka swsusp).
1800  */
1801 int swap_type_of(dev_t device, sector_t offset)
1802 {
1803         int type;
1804 
1805         if (!device)
1806                 return -1;
1807 
1808         spin_lock(&swap_lock);
1809         for (type = 0; type < nr_swapfiles; type++) {
1810                 struct swap_info_struct *sis = swap_info[type];
1811 
1812                 if (!(sis->flags & SWP_WRITEOK))
1813                         continue;
1814 
1815                 if (device == sis->bdev->bd_dev) {
1816                         struct swap_extent *se = first_se(sis);
1817 
1818                         if (se->start_block == offset) {
1819                                 spin_unlock(&swap_lock);
1820                                 return type;
1821                         }
1822                 }
1823         }
1824         spin_unlock(&swap_lock);
1825         return -ENODEV;
1826 }
1827 
1828 int find_first_swap(dev_t *device)
1829 {
1830         int type;
1831 
1832         spin_lock(&swap_lock);
1833         for (type = 0; type < nr_swapfiles; type++) {
1834                 struct swap_info_struct *sis = swap_info[type];
1835 
1836                 if (!(sis->flags & SWP_WRITEOK))
1837                         continue;
1838                 *device = sis->bdev->bd_dev;
1839                 spin_unlock(&swap_lock);
1840                 return type;
1841         }
1842         spin_unlock(&swap_lock);
1843         return -ENODEV;
1844 }
1845 
1846 /*
1847  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1848  * corresponding to given index in swap_info (swap type).
1849  */
1850 sector_t swapdev_block(int type, pgoff_t offset)
1851 {
1852         struct swap_info_struct *si = swap_type_to_swap_info(type);
1853         struct swap_extent *se;
1854 
1855         if (!si || !(si->flags & SWP_WRITEOK))
1856                 return 0;
1857         se = offset_to_swap_extent(si, offset);
1858         return se->start_block + (offset - se->start_page);
1859 }
1860 
1861 /*
1862  * Return either the total number of swap pages of given type, or the number
1863  * of free pages of that type (depending on @free)
1864  *
1865  * This is needed for software suspend
1866  */
1867 unsigned int count_swap_pages(int type, int free)
1868 {
1869         unsigned int n = 0;
1870 
1871         spin_lock(&swap_lock);
1872         if ((unsigned int)type < nr_swapfiles) {
1873                 struct swap_info_struct *sis = swap_info[type];
1874 
1875                 spin_lock(&sis->lock);
1876                 if (sis->flags & SWP_WRITEOK) {
1877                         n = sis->pages;
1878                         if (free)
1879                                 n -= sis->inuse_pages;
1880                 }
1881                 spin_unlock(&sis->lock);
1882         }
1883         spin_unlock(&swap_lock);
1884         return n;
1885 }
1886 #endif /* CONFIG_HIBERNATION */
1887 
1888 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
1889 {
1890         return pte_same(pte_swp_clear_flags(pte), swp_pte);
1891 }
1892 
1893 /*
1894  * No need to decide whether this PTE shares the swap entry with others,
1895  * just let do_wp_page work it out if a write is requested later - to
1896  * force COW, vm_page_prot omits write permission from any private vma.
1897  */
1898 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
1899                 unsigned long addr, swp_entry_t entry, struct page *page)
1900 {
1901         struct page *swapcache;
1902         spinlock_t *ptl;
1903         pte_t *pte;
1904         int ret = 1;
1905 
1906         swapcache = page;
1907         page = ksm_might_need_to_copy(page, vma, addr);
1908         if (unlikely(!page))
1909                 return -ENOMEM;
1910 
1911         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
1912         if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
1913                 ret = 0;
1914                 goto out;
1915         }
1916 
1917         dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
1918         inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
1919         get_page(page);
1920         set_pte_at(vma->vm_mm, addr, pte,
1921                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
1922         if (page == swapcache) {
1923                 page_add_anon_rmap(page, vma, addr, false);
1924         } else { /* ksm created a completely new copy */
1925                 page_add_new_anon_rmap(page, vma, addr, false);
1926                 lru_cache_add_inactive_or_unevictable(page, vma);
1927         }
1928         swap_free(entry);
1929 out:
1930         pte_unmap_unlock(pte, ptl);
1931         if (page != swapcache) {
1932                 unlock_page(page);
1933                 put_page(page);
1934         }
1935         return ret;
1936 }
1937 
1938 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
1939                         unsigned long addr, unsigned long end,
1940                         unsigned int type, bool frontswap,
1941                         unsigned long *fs_pages_to_unuse)
1942 {
1943         struct page *page;
1944         swp_entry_t entry;
1945         pte_t *pte;
1946         struct swap_info_struct *si;
1947         unsigned long offset;
1948         int ret = 0;
1949         volatile unsigned char *swap_map;
1950 
1951         si = swap_info[type];
1952         pte = pte_offset_map(pmd, addr);
1953         do {
1954                 if (!is_swap_pte(*pte))
1955                         continue;
1956 
1957                 entry = pte_to_swp_entry(*pte);
1958                 if (swp_type(entry) != type)
1959                         continue;
1960 
1961                 offset = swp_offset(entry);
1962                 if (frontswap && !frontswap_test(si, offset))
1963                         continue;
1964 
1965                 pte_unmap(pte);
1966                 swap_map = &si->swap_map[offset];
1967                 page = lookup_swap_cache(entry, vma, addr);
1968                 if (!page) {
1969                         struct vm_fault vmf = {
1970                                 .vma = vma,
1971                                 .address = addr,
1972                                 .pmd = pmd,
1973                         };
1974 
1975                         page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
1976                                                 &vmf);
1977                 }
1978                 if (!page) {
1979                         if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
1980                                 goto try_next;
1981                         return -ENOMEM;
1982                 }
1983 
1984                 lock_page(page);
1985                 wait_on_page_writeback(page);
1986                 ret = unuse_pte(vma, pmd, addr, entry, page);
1987                 if (ret < 0) {
1988                         unlock_page(page);
1989                         put_page(page);
1990                         goto out;
1991                 }
1992 
1993                 try_to_free_swap(page);
1994                 unlock_page(page);
1995                 put_page(page);
1996 
1997                 if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
1998                         ret = FRONTSWAP_PAGES_UNUSED;
1999                         goto out;
2000                 }
2001 try_next:
2002                 pte = pte_offset_map(pmd, addr);
2003         } while (pte++, addr += PAGE_SIZE, addr != end);
2004         pte_unmap(pte - 1);
2005 
2006         ret = 0;
2007 out:
2008         return ret;
2009 }
2010 
2011 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
2012                                 unsigned long addr, unsigned long end,
2013                                 unsigned int type, bool frontswap,
2014                                 unsigned long *fs_pages_to_unuse)
2015 {
2016         pmd_t *pmd;
2017         unsigned long next;
2018         int ret;
2019 
2020         pmd = pmd_offset(pud, addr);
2021         do {
2022                 cond_resched();
2023                 next = pmd_addr_end(addr, end);
2024                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
2025                         continue;
2026                 ret = unuse_pte_range(vma, pmd, addr, next, type,
2027                                       frontswap, fs_pages_to_unuse);
2028                 if (ret)
2029                         return ret;
2030         } while (pmd++, addr = next, addr != end);
2031         return 0;
2032 }
2033 
2034 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
2035                                 unsigned long addr, unsigned long end,
2036                                 unsigned int type, bool frontswap,
2037                                 unsigned long *fs_pages_to_unuse)
2038 {
2039         pud_t *pud;
2040         unsigned long next;
2041         int ret;
2042 
2043         pud = pud_offset(p4d, addr);
2044         do {
2045                 next = pud_addr_end(addr, end);
2046                 if (pud_none_or_clear_bad(pud))
2047                         continue;
2048                 ret = unuse_pmd_range(vma, pud, addr, next, type,
2049                                       frontswap, fs_pages_to_unuse);
2050                 if (ret)
2051                         return ret;
2052         } while (pud++, addr = next, addr != end);
2053         return 0;
2054 }
2055 
2056 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
2057                                 unsigned long addr, unsigned long end,
2058                                 unsigned int type, bool frontswap,
2059                                 unsigned long *fs_pages_to_unuse)
2060 {
2061         p4d_t *p4d;
2062         unsigned long next;
2063         int ret;
2064 
2065         p4d = p4d_offset(pgd, addr);
2066         do {
2067                 next = p4d_addr_end(addr, end);
2068                 if (p4d_none_or_clear_bad(p4d))
2069                         continue;
2070                 ret = unuse_pud_range(vma, p4d, addr, next, type,
2071                                       frontswap, fs_pages_to_unuse);
2072                 if (ret)
2073                         return ret;
2074         } while (p4d++, addr = next, addr != end);
2075         return 0;
2076 }
2077 
2078 static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
2079                      bool frontswap, unsigned long *fs_pages_to_unuse)
2080 {
2081         pgd_t *pgd;
2082         unsigned long addr, end, next;
2083         int ret;
2084 
2085         addr = vma->vm_start;
2086         end = vma->vm_end;
2087 
2088         pgd = pgd_offset(vma->vm_mm, addr);
2089         do {
2090                 next = pgd_addr_end(addr, end);
2091                 if (pgd_none_or_clear_bad(pgd))
2092                         continue;
2093                 ret = unuse_p4d_range(vma, pgd, addr, next, type,
2094                                       frontswap, fs_pages_to_unuse);
2095                 if (ret)
2096                         return ret;
2097         } while (pgd++, addr = next, addr != end);
2098         return 0;
2099 }
2100 
2101 static int unuse_mm(struct mm_struct *mm, unsigned int type,
2102                     bool frontswap, unsigned long *fs_pages_to_unuse)
2103 {
2104         struct vm_area_struct *vma;
2105         int ret = 0;
2106 
2107         mmap_read_lock(mm);
2108         for (vma = mm->mmap; vma; vma = vma->vm_next) {
2109                 if (vma->anon_vma) {
2110                         ret = unuse_vma(vma, type, frontswap,
2111                                         fs_pages_to_unuse);
2112                         if (ret)
2113                                 break;
2114                 }
2115                 cond_resched();
2116         }
2117         mmap_read_unlock(mm);
2118         return ret;
2119 }
2120 
2121 /*
2122  * Scan swap_map (or frontswap_map if frontswap parameter is true)
2123  * from current position to next entry still in use. Return 0
2124  * if there are no inuse entries after prev till end of the map.
2125  */
2126 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
2127                                         unsigned int prev, bool frontswap)
2128 {
2129         unsigned int i;
2130         unsigned char count;
2131 
2132         /*
2133          * No need for swap_lock here: we're just looking
2134          * for whether an entry is in use, not modifying it; false
2135          * hits are okay, and sys_swapoff() has already prevented new
2136          * allocations from this area (while holding swap_lock).
2137          */
2138         for (i = prev + 1; i < si->max; i++) {
2139                 count = READ_ONCE(si->swap_map[i]);
2140                 if (count && swap_count(count) != SWAP_MAP_BAD)
2141                         if (!frontswap || frontswap_test(si, i))
2142                                 break;
2143                 if ((i % LATENCY_LIMIT) == 0)
2144                         cond_resched();
2145         }
2146 
2147         if (i == si->max)
2148                 i = 0;
2149 
2150         return i;
2151 }
2152 
2153 /*
2154  * If the boolean frontswap is true, only unuse pages_to_unuse pages;
2155  * pages_to_unuse==0 means all pages; ignored if frontswap is false
2156  */
2157 int try_to_unuse(unsigned int type, bool frontswap,
2158                  unsigned long pages_to_unuse)
2159 {
2160         struct mm_struct *prev_mm;
2161         struct mm_struct *mm;
2162         struct list_head *p;
2163         int retval = 0;
2164         struct swap_info_struct *si = swap_info[type];
2165         struct page *page;
2166         swp_entry_t entry;
2167         unsigned int i;
2168 
2169         if (!READ_ONCE(si->inuse_pages))
2170                 return 0;
2171 
2172         if (!frontswap)
2173                 pages_to_unuse = 0;
2174 
2175 retry:
2176         retval = shmem_unuse(type, frontswap, &pages_to_unuse);
2177         if (retval)
2178                 goto out;
2179 
2180         prev_mm = &init_mm;
2181         mmget(prev_mm);
2182 
2183         spin_lock(&mmlist_lock);
2184         p = &init_mm.mmlist;
2185         while (READ_ONCE(si->inuse_pages) &&
2186                !signal_pending(current) &&
2187                (p = p->next) != &init_mm.mmlist) {
2188 
2189                 mm = list_entry(p, struct mm_struct, mmlist);
2190                 if (!mmget_not_zero(mm))
2191                         continue;
2192                 spin_unlock(&mmlist_lock);
2193                 mmput(prev_mm);
2194                 prev_mm = mm;
2195                 retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
2196 
2197                 if (retval) {
2198                         mmput(prev_mm);
2199                         goto out;
2200                 }
2201 
2202                 /*
2203                  * Make sure that we aren't completely killing
2204                  * interactive performance.
2205                  */
2206                 cond_resched();
2207                 spin_lock(&mmlist_lock);
2208         }
2209         spin_unlock(&mmlist_lock);
2210 
2211         mmput(prev_mm);
2212 
2213         i = 0;
2214         while (READ_ONCE(si->inuse_pages) &&
2215                !signal_pending(current) &&
2216                (i = find_next_to_unuse(si, i, frontswap)) != 0) {
2217 
2218                 entry = swp_entry(type, i);
2219                 page = find_get_page(swap_address_space(entry), i);
2220                 if (!page)
2221                         continue;
2222 
2223                 /*
2224                  * It is conceivable that a racing task removed this page from
2225                  * swap cache just before we acquired the page lock. The page
2226                  * might even be back in swap cache on another swap area. But
2227                  * that is okay, try_to_free_swap() only removes stale pages.
2228                  */
2229                 lock_page(page);
2230                 wait_on_page_writeback(page);
2231                 try_to_free_swap(page);
2232                 unlock_page(page);
2233                 put_page(page);
2234 
2235                 /*
2236                  * For frontswap, we just need to unuse pages_to_unuse, if
2237                  * it was specified. Need not check frontswap again here as
2238                  * we already zeroed out pages_to_unuse if not frontswap.
2239                  */
2240                 if (pages_to_unuse && --pages_to_unuse == 0)
2241                         goto out;
2242         }
2243 
2244         /*
2245          * Lets check again to see if there are still swap entries in the map.
2246          * If yes, we would need to do retry the unuse logic again.
2247          * Under global memory pressure, swap entries can be reinserted back
2248          * into process space after the mmlist loop above passes over them.
2249          *
2250          * Limit the number of retries? No: when mmget_not_zero() above fails,
2251          * that mm is likely to be freeing swap from exit_mmap(), which proceeds
2252          * at its own independent pace; and even shmem_writepage() could have
2253          * been preempted after get_swap_page(), temporarily hiding that swap.
2254          * It's easy and robust (though cpu-intensive) just to keep retrying.
2255          */
2256         if (READ_ONCE(si->inuse_pages)) {
2257                 if (!signal_pending(current))
2258                         goto retry;
2259                 retval = -EINTR;
2260         }
2261 out:
2262         return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
2263 }
2264 
2265 /*
2266  * After a successful try_to_unuse, if no swap is now in use, we know
2267  * we can empty the mmlist.  swap_lock must be held on entry and exit.
2268  * Note that mmlist_lock nests inside swap_lock, and an mm must be
2269  * added to the mmlist just after page_duplicate - before would be racy.
2270  */
2271 static void drain_mmlist(void)
2272 {
2273         struct list_head *p, *next;
2274         unsigned int type;
2275 
2276         for (type = 0; type < nr_swapfiles; type++)
2277                 if (swap_info[type]->inuse_pages)
2278                         return;
2279         spin_lock(&mmlist_lock);
2280         list_for_each_safe(p, next, &init_mm.mmlist)
2281                 list_del_init(p);
2282         spin_unlock(&mmlist_lock);
2283 }
2284 
2285 /*
2286  * Free all of a swapdev's extent information
2287  */
2288 static void destroy_swap_extents(struct swap_info_struct *sis)
2289 {
2290         while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
2291                 struct rb_node *rb = sis->swap_extent_root.rb_node;
2292                 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
2293 
2294                 rb_erase(rb, &sis->swap_extent_root);
2295                 kfree(se);
2296         }
2297 
2298         if (sis->flags & SWP_ACTIVATED) {
2299                 struct file *swap_file = sis->swap_file;
2300                 struct address_space *mapping = swap_file->f_mapping;
2301 
2302                 sis->flags &= ~SWP_ACTIVATED;
2303                 if (mapping->a_ops->swap_deactivate)
2304                         mapping->a_ops->swap_deactivate(swap_file);
2305         }
2306 }
2307 
2308 /*
2309  * Add a block range (and the corresponding page range) into this swapdev's
2310  * extent tree.
2311  *
2312  * This function rather assumes that it is called in ascending page order.
2313  */
2314 int
2315 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
2316                 unsigned long nr_pages, sector_t start_block)
2317 {
2318         struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
2319         struct swap_extent *se;
2320         struct swap_extent *new_se;
2321 
2322         /*
2323          * place the new node at the right most since the
2324          * function is called in ascending page order.
2325          */
2326         while (*link) {
2327                 parent = *link;
2328                 link = &parent->rb_right;
2329         }
2330 
2331         if (parent) {
2332                 se = rb_entry(parent, struct swap_extent, rb_node);
2333                 BUG_ON(se->start_page + se->nr_pages != start_page);
2334                 if (se->start_block + se->nr_pages == start_block) {
2335                         /* Merge it */
2336                         se->nr_pages += nr_pages;
2337                         return 0;
2338                 }
2339         }
2340 
2341         /* No merge, insert a new extent. */
2342         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
2343         if (new_se == NULL)
2344                 return -ENOMEM;
2345         new_se->start_page = start_page;
2346         new_se->nr_pages = nr_pages;
2347         new_se->start_block = start_block;
2348 
2349         rb_link_node(&new_se->rb_node, parent, link);
2350         rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
2351         return 1;
2352 }
2353 EXPORT_SYMBOL_GPL(add_swap_extent);
2354 
2355 /*
2356  * A `swap extent' is a simple thing which maps a contiguous range of pages
2357  * onto a contiguous range of disk blocks.  An ordered list of swap extents
2358  * is built at swapon time and is then used at swap_writepage/swap_readpage
2359  * time for locating where on disk a page belongs.
2360  *
2361  * If the swapfile is an S_ISBLK block device, a single extent is installed.
2362  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
2363  * swap files identically.
2364  *
2365  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
2366  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
2367  * swapfiles are handled *identically* after swapon time.
2368  *
2369  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
2370  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
2371  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
2372  * requirements, they are simply tossed out - we will never use those blocks
2373  * for swapping.
2374  *
2375  * For all swap devices we set S_SWAPFILE across the life of the swapon.  This
2376  * prevents users from writing to the swap device, which will corrupt memory.
2377  *
2378  * The amount of disk space which a single swap extent represents varies.
2379  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
2380  * extents in the list.  To avoid much list walking, we cache the previous
2381  * search location in `curr_swap_extent', and start new searches from there.
2382  * This is extremely effective.  The average number of iterations in
2383  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
2384  */
2385 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
2386 {
2387         struct file *swap_file = sis->swap_file;
2388         struct address_space *mapping = swap_file->f_mapping;
2389         struct inode *inode = mapping->host;
2390         int ret;
2391 
2392         if (S_ISBLK(inode->i_mode)) {
2393                 ret = add_swap_extent(sis, 0, sis->max, 0);
2394                 *span = sis->pages;
2395                 return ret;
2396         }
2397 
2398         if (mapping->a_ops->swap_activate) {
2399                 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
2400                 if (ret >= 0)
2401                         sis->flags |= SWP_ACTIVATED;
2402                 if (!ret) {
2403                         sis->flags |= SWP_FS_OPS;
2404                         ret = add_swap_extent(sis, 0, sis->max, 0);
2405                         *span = sis->pages;
2406                 }
2407                 return ret;
2408         }
2409 
2410         return generic_swapfile_activate(sis, swap_file, span);
2411 }
2412 
2413 static int swap_node(struct swap_info_struct *p)
2414 {
2415         struct block_device *bdev;
2416 
2417         if (p->bdev)
2418                 bdev = p->bdev;
2419         else
2420                 bdev = p->swap_file->f_inode->i_sb->s_bdev;
2421 
2422         return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
2423 }
2424 
2425 static void setup_swap_info(struct swap_info_struct *p, int prio,
2426                             unsigned char *swap_map,
2427                             struct swap_cluster_info *cluster_info)
2428 {
2429         int i;
2430 
2431         if (prio >= 0)
2432                 p->prio = prio;
2433         else
2434                 p->prio = --least_priority;
2435         /*
2436          * the plist prio is negated because plist ordering is
2437          * low-to-high, while swap ordering is high-to-low
2438          */
2439         p->list.prio = -p->prio;
2440         for_each_node(i) {
2441                 if (p->prio >= 0)
2442                         p->avail_lists[i].prio = -p->prio;
2443                 else {
2444                         if (swap_node(p) == i)
2445                                 p->avail_lists[i].prio = 1;
2446                         else
2447                                 p->avail_lists[i].prio = -p->prio;
2448                 }
2449         }
2450         p->swap_map = swap_map;
2451         p->cluster_info = cluster_info;
2452 }
2453 
2454 static void _enable_swap_info(struct swap_info_struct *p)
2455 {
2456         p->flags |= SWP_WRITEOK;
2457         atomic_long_add(p->pages, &nr_swap_pages);
2458         total_swap_pages += p->pages;
2459 
2460         assert_spin_locked(&swap_lock);
2461         /*
2462          * both lists are plists, and thus priority ordered.
2463          * swap_active_head needs to be priority ordered for swapoff(),
2464          * which on removal of any swap_info_struct with an auto-assigned
2465          * (i.e. negative) priority increments the auto-assigned priority
2466          * of any lower-priority swap_info_structs.
2467          * swap_avail_head needs to be priority ordered for get_swap_page(),
2468          * which allocates swap pages from the highest available priority
2469          * swap_info_struct.
2470          */
2471         plist_add(&p->list, &swap_active_head);
2472         add_to_avail_list(p);
2473 }
2474 
2475 static void enable_swap_info(struct swap_info_struct *p, int prio,
2476                                 unsigned char *swap_map,
2477                                 struct swap_cluster_info *cluster_info,
2478                                 unsigned long *frontswap_map)
2479 {
2480         frontswap_init(p->type, frontswap_map);
2481         spin_lock(&swap_lock);
2482         spin_lock(&p->lock);
2483         setup_swap_info(p, prio, swap_map, cluster_info);
2484         spin_unlock(&p->lock);
2485         spin_unlock(&swap_lock);
2486         /*
2487          * Finished initializing swap device, now it's safe to reference it.
2488          */
2489         percpu_ref_resurrect(&p->users);
2490         spin_lock(&swap_lock);
2491         spin_lock(&p->lock);
2492         _enable_swap_info(p);
2493         spin_unlock(&p->lock);
2494         spin_unlock(&swap_lock);
2495 }
2496 
2497 static void reinsert_swap_info(struct swap_info_struct *p)
2498 {
2499         spin_lock(&swap_lock);
2500         spin_lock(&p->lock);
2501         setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
2502         _enable_swap_info(p);
2503         spin_unlock(&p->lock);
2504         spin_unlock(&swap_lock);
2505 }
2506 
2507 bool has_usable_swap(void)
2508 {
2509         bool ret = true;
2510 
2511         spin_lock(&swap_lock);
2512         if (plist_head_empty(&swap_active_head))
2513                 ret = false;
2514         spin_unlock(&swap_lock);
2515         return ret;
2516 }
2517 
2518 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
2519 {
2520         struct swap_info_struct *p = NULL;
2521         unsigned char *swap_map;
2522         struct swap_cluster_info *cluster_info;
2523         unsigned long *frontswap_map;
2524         struct file *swap_file, *victim;
2525         struct address_space *mapping;
2526         struct inode *inode;
2527         struct filename *pathname;
2528         int err, found = 0;
2529         unsigned int old_block_size;
2530 
2531         if (!capable(CAP_SYS_ADMIN))
2532                 return -EPERM;
2533 
2534         BUG_ON(!current->mm);
2535 
2536         pathname = getname(specialfile);
2537         if (IS_ERR(pathname))
2538                 return PTR_ERR(pathname);
2539 
2540         victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
2541         err = PTR_ERR(victim);
2542         if (IS_ERR(victim))
2543                 goto out;
2544 
2545         mapping = victim->f_mapping;
2546         spin_lock(&swap_lock);
2547         plist_for_each_entry(p, &swap_active_head, list) {
2548                 if (p->flags & SWP_WRITEOK) {
2549                         if (p->swap_file->f_mapping == mapping) {
2550                                 found = 1;
2551                                 break;
2552                         }
2553                 }
2554         }
2555         if (!found) {
2556                 err = -EINVAL;
2557                 spin_unlock(&swap_lock);
2558                 goto out_dput;
2559         }
2560         if (!security_vm_enough_memory_mm(current->mm, p->pages))
2561                 vm_unacct_memory(p->pages);
2562         else {
2563                 err = -ENOMEM;
2564                 spin_unlock(&swap_lock);
2565                 goto out_dput;
2566         }
2567         del_from_avail_list(p);
2568         spin_lock(&p->lock);
2569         if (p->prio < 0) {
2570                 struct swap_info_struct *si = p;
2571                 int nid;
2572 
2573                 plist_for_each_entry_continue(si, &swap_active_head, list) {
2574                         si->prio++;
2575                         si->list.prio--;
2576                         for_each_node(nid) {
2577                                 if (si->avail_lists[nid].prio != 1)
2578                                         si->avail_lists[nid].prio--;
2579                         }
2580                 }
2581                 least_priority++;
2582         }
2583         plist_del(&p->list, &swap_active_head);
2584         atomic_long_sub(p->pages, &nr_swap_pages);
2585         total_swap_pages -= p->pages;
2586         p->flags &= ~SWP_WRITEOK;
2587         spin_unlock(&p->lock);
2588         spin_unlock(&swap_lock);
2589 
2590         disable_swap_slots_cache_lock();
2591 
2592         set_current_oom_origin();
2593         err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
2594         clear_current_oom_origin();
2595 
2596         if (err) {
2597                 /* re-insert swap space back into swap_list */
2598                 reinsert_swap_info(p);
2599                 reenable_swap_slots_cache_unlock();
2600                 goto out_dput;
2601         }
2602 
2603         reenable_swap_slots_cache_unlock();
2604 
2605         /*
2606          * Wait for swap operations protected by get/put_swap_device()
2607          * to complete.
2608          *
2609          * We need synchronize_rcu() here to protect the accessing to
2610          * the swap cache data structure.
2611          */
2612         percpu_ref_kill(&p->users);
2613         synchronize_rcu();
2614         wait_for_completion(&p->comp);
2615 
2616         flush_work(&p->discard_work);
2617 
2618         destroy_swap_extents(p);
2619         if (p->flags & SWP_CONTINUED)
2620                 free_swap_count_continuations(p);
2621 
2622         if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
2623                 atomic_dec(&nr_rotate_swap);
2624 
2625         mutex_lock(&swapon_mutex);
2626         spin_lock(&swap_lock);
2627         spin_lock(&p->lock);
2628         drain_mmlist();
2629 
2630         /* wait for anyone still in scan_swap_map_slots */
2631         p->highest_bit = 0;             /* cuts scans short */
2632         while (p->flags >= SWP_SCANNING) {
2633                 spin_unlock(&p->lock);
2634                 spin_unlock(&swap_lock);
2635                 schedule_timeout_uninterruptible(1);
2636                 spin_lock(&swap_lock);
2637                 spin_lock(&p->lock);
2638         }
2639 
2640         swap_file = p->swap_file;
2641         old_block_size = p->old_block_size;
2642         p->swap_file = NULL;
2643         p->max = 0;
2644         swap_map = p->swap_map;
2645         p->swap_map = NULL;
2646         cluster_info = p->cluster_info;
2647         p->cluster_info = NULL;
2648         frontswap_map = frontswap_map_get(p);
2649         spin_unlock(&p->lock);
2650         spin_unlock(&swap_lock);
2651         arch_swap_invalidate_area(p->type);
2652         frontswap_invalidate_area(p->type);
2653         frontswap_map_set(p, NULL);
2654         mutex_unlock(&swapon_mutex);
2655         free_percpu(p->percpu_cluster);
2656         p->percpu_cluster = NULL;
2657         free_percpu(p->cluster_next_cpu);
2658         p->cluster_next_cpu = NULL;
2659         vfree(swap_map);
2660         kvfree(cluster_info);
2661         kvfree(frontswap_map);
2662         /* Destroy swap account information */
2663         swap_cgroup_swapoff(p->type);
2664         exit_swap_address_space(p->type);
2665 
2666         inode = mapping->host;
2667         if (S_ISBLK(inode->i_mode)) {
2668                 struct block_device *bdev = I_BDEV(inode);
2669 
2670                 set_blocksize(bdev, old_block_size);
2671                 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
2672         }
2673 
2674         inode_lock(inode);
2675         inode->i_flags &= ~S_SWAPFILE;
2676         inode_unlock(inode);
2677         filp_close(swap_file, NULL);
2678 
2679         /*
2680          * Clear the SWP_USED flag after all resources are freed so that swapon
2681          * can reuse this swap_info in alloc_swap_info() safely.  It is ok to
2682          * not hold p->lock after we cleared its SWP_WRITEOK.
2683          */
2684         spin_lock(&swap_lock);
2685         p->flags = 0;
2686         spin_unlock(&swap_lock);
2687 
2688         err = 0;
2689         atomic_inc(&proc_poll_event);
2690         wake_up_interruptible(&proc_poll_wait);
2691 
2692 out_dput:
2693         filp_close(victim, NULL);
2694 out:
2695         putname(pathname);
2696         return err;
2697 }
2698 
2699 #ifdef CONFIG_PROC_FS
2700 static __poll_t swaps_poll(struct file *file, poll_table *wait)
2701 {
2702         struct seq_file *seq = file->private_data;
2703 
2704         poll_wait(file, &proc_poll_wait, wait);
2705 
2706         if (seq->poll_event != atomic_read(&proc_poll_event)) {
2707                 seq->poll_event = atomic_read(&proc_poll_event);
2708                 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
2709         }
2710 
2711         return EPOLLIN | EPOLLRDNORM;
2712 }
2713 
2714 /* iterator */
2715 static void *swap_start(struct seq_file *swap, loff_t *pos)
2716 {
2717         struct swap_info_struct *si;
2718         int type;
2719         loff_t l = *pos;
2720 
2721         mutex_lock(&swapon_mutex);
2722 
2723         if (!l)
2724                 return SEQ_START_TOKEN;
2725 
2726         for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
2727                 if (!(si->flags & SWP_USED) || !si->swap_map)
2728                         continue;
2729                 if (!--l)
2730                         return si;
2731         }
2732 
2733         return NULL;
2734 }
2735 
2736 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
2737 {
2738         struct swap_info_struct *si = v;
2739         int type;
2740 
2741         if (v == SEQ_START_TOKEN)
2742                 type = 0;
2743         else
2744                 type = si->type + 1;
2745 
2746         ++(*pos);
2747         for (; (si = swap_type_to_swap_info(type)); type++) {
2748                 if (!(si->flags & SWP_USED) || !si->swap_map)
2749                         continue;
2750                 return si;
2751         }
2752 
2753         return NULL;
2754 }
2755 
2756 static void swap_stop(struct seq_file *swap, void *v)
2757 {
2758         mutex_unlock(&swapon_mutex);
2759 }
2760 
2761 static int swap_show(struct seq_file *swap, void *v)
2762 {
2763         struct swap_info_struct *si = v;
2764         struct file *file;
2765         int len;
2766         unsigned long bytes, inuse;
2767 
2768         if (si == SEQ_START_TOKEN) {
2769                 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
2770                 return 0;
2771         }
2772 
2773         bytes = si->pages << (PAGE_SHIFT - 10);
2774         inuse = si->inuse_pages << (PAGE_SHIFT - 10);
2775 
2776         file = si->swap_file;
2777         len = seq_file_path(swap, file, " \t\n\\");
2778         seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n",
2779                         len < 40 ? 40 - len : 1, " ",
2780                         S_ISBLK(file_inode(file)->i_mode) ?
2781                                 "partition" : "file\t",
2782                         bytes, bytes < 10000000 ? "\t" : "",
2783                         inuse, inuse < 10000000 ? "\t" : "",
2784                         si->prio);
2785         return 0;
2786 }
2787 
2788 static const struct seq_operations swaps_op = {
2789         .start =        swap_start,
2790         .next =         swap_next,
2791         .stop =         swap_stop,
2792         .show =         swap_show
2793 };
2794 
2795 static int swaps_open(struct inode *inode, struct file *file)
2796 {
2797         struct seq_file *seq;
2798         int ret;
2799 
2800         ret = seq_open(file, &swaps_op);
2801         if (ret)
2802                 return ret;
2803 
2804         seq = file->private_data;
2805         seq->poll_event = atomic_read(&proc_poll_event);
2806         return 0;
2807 }
2808 
2809 static const struct proc_ops swaps_proc_ops = {
2810         .proc_flags     = PROC_ENTRY_PERMANENT,
2811         .proc_open      = swaps_open,
2812         .proc_read      = seq_read,
2813         .proc_lseek     = seq_lseek,
2814         .proc_release   = seq_release,
2815         .proc_poll      = swaps_poll,
2816 };
2817 
2818 static int __init procswaps_init(void)
2819 {
2820         proc_create("swaps", 0, NULL, &swaps_proc_ops);
2821         return 0;
2822 }
2823 __initcall(procswaps_init);
2824 #endif /* CONFIG_PROC_FS */
2825 
2826 #ifdef MAX_SWAPFILES_CHECK
2827 static int __init max_swapfiles_check(void)
2828 {
2829         MAX_SWAPFILES_CHECK();
2830         return 0;
2831 }
2832 late_initcall(max_swapfiles_check);
2833 #endif
2834 
2835 static struct swap_info_struct *alloc_swap_info(void)
2836 {
2837         struct swap_info_struct *p;
2838         struct swap_info_struct *defer = NULL;
2839         unsigned int type;
2840         int i;
2841 
2842         p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
2843         if (!p)
2844                 return ERR_PTR(-ENOMEM);
2845 
2846         if (percpu_ref_init(&p->users, swap_users_ref_free,
2847                             PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
2848                 kvfree(p);
2849                 return ERR_PTR(-ENOMEM);
2850         }
2851 
2852         spin_lock(&swap_lock);
2853         for (type = 0; type < nr_swapfiles; type++) {
2854                 if (!(swap_info[type]->flags & SWP_USED))
2855                         break;
2856         }
2857         if (type >= MAX_SWAPFILES) {
2858                 spin_unlock(&swap_lock);
2859                 percpu_ref_exit(&p->users);
2860                 kvfree(p);
2861                 return ERR_PTR(-EPERM);
2862         }
2863         if (type >= nr_swapfiles) {
2864                 p->type = type;
2865                 /*
2866                  * Publish the swap_info_struct after initializing it.
2867                  * Note that kvzalloc() above zeroes all its fields.
2868                  */
2869                 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
2870                 nr_swapfiles++;
2871         } else {
2872                 defer = p;
2873                 p = swap_info[type];
2874                 /*
2875                  * Do not memset this entry: a racing procfs swap_next()
2876                  * would be relying on p->type to remain valid.
2877                  */
2878         }
2879         p->swap_extent_root = RB_ROOT;
2880         plist_node_init(&p->list, 0);
2881         for_each_node(i)
2882                 plist_node_init(&p->avail_lists[i], 0);
2883         p->flags = SWP_USED;
2884         spin_unlock(&swap_lock);
2885         if (defer) {
2886                 percpu_ref_exit(&defer->users);
2887                 kvfree(defer);
2888         }
2889         spin_lock_init(&p->lock);
2890         spin_lock_init(&p->cont_lock);
2891         init_completion(&p->comp);
2892 
2893         return p;
2894 }
2895 
2896 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
2897 {
2898         int error;
2899 
2900         if (S_ISBLK(inode->i_mode)) {
2901                 p->bdev = blkdev_get_by_dev(inode->i_rdev,
2902                                    FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
2903                 if (IS_ERR(p->bdev)) {
2904                         error = PTR_ERR(p->bdev);
2905                         p->bdev = NULL;
2906                         return error;
2907                 }
2908                 p->old_block_size = block_size(p->bdev);
2909                 error = set_blocksize(p->bdev, PAGE_SIZE);
2910                 if (error < 0)
2911                         return error;
2912                 /*
2913                  * Zoned block devices contain zones that have a sequential
2914                  * write only restriction.  Hence zoned block devices are not
2915                  * suitable for swapping.  Disallow them here.
2916                  */
2917                 if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
2918                         return -EINVAL;
2919                 p->flags |= SWP_BLKDEV;
2920         } else if (S_ISREG(inode->i_mode)) {
2921                 p->bdev = inode->i_sb->s_bdev;
2922         }
2923 
2924         return 0;
2925 }
2926 
2927 
2928 /*
2929  * Find out how many pages are allowed for a single swap device. There
2930  * are two limiting factors:
2931  * 1) the number of bits for the swap offset in the swp_entry_t type, and
2932  * 2) the number of bits in the swap pte, as defined by the different
2933  * architectures.
2934  *
2935  * In order to find the largest possible bit mask, a swap entry with
2936  * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
2937  * decoded to a swp_entry_t again, and finally the swap offset is
2938  * extracted.
2939  *
2940  * This will mask all the bits from the initial ~0UL mask that can't
2941  * be encoded in either the swp_entry_t or the architecture definition
2942  * of a swap pte.
2943  */
2944 unsigned long generic_max_swapfile_size(void)
2945 {
2946         return swp_offset(pte_to_swp_entry(
2947                         swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2948 }
2949 
2950 /* Can be overridden by an architecture for additional checks. */
2951 __weak unsigned long max_swapfile_size(void)
2952 {
2953         return generic_max_swapfile_size();
2954 }
2955 
2956 static unsigned long read_swap_header(struct swap_info_struct *p,
2957                                         union swap_header *swap_header,
2958                                         struct inode *inode)
2959 {
2960         int i;
2961         unsigned long maxpages;
2962         unsigned long swapfilepages;
2963         unsigned long last_page;
2964 
2965         if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
2966                 pr_err("Unable to find swap-space signature\n");
2967                 return 0;
2968         }
2969 
2970         /* swap partition endianness hack... */
2971         if (swab32(swap_header->info.version) == 1) {
2972                 swab32s(&swap_header->info.version);
2973                 swab32s(&swap_header->info.last_page);
2974                 swab32s(&swap_header->info.nr_badpages);
2975                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2976                         return 0;
2977                 for (i = 0; i < swap_header->info.nr_badpages; i++)
2978                         swab32s(&swap_header->info.badpages[i]);
2979         }
2980         /* Check the swap header's sub-version */
2981         if (swap_header->info.version != 1) {
2982                 pr_warn("Unable to handle swap header version %d\n",
2983                         swap_header->info.version);
2984                 return 0;
2985         }
2986 
2987         p->lowest_bit  = 1;
2988         p->cluster_next = 1;
2989         p->cluster_nr = 0;
2990 
2991         maxpages = max_swapfile_size();
2992         last_page = swap_header->info.last_page;
2993         if (!last_page) {
2994                 pr_warn("Empty swap-file\n");
2995                 return 0;
2996         }
2997         if (last_page > maxpages) {
2998                 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
2999                         maxpages << (PAGE_SHIFT - 10),
3000                         last_page << (PAGE_SHIFT - 10));
3001         }
3002         if (maxpages > last_page) {
3003                 maxpages = last_page + 1;
3004                 /* p->max is an unsigned int: don't overflow it */
3005                 if ((unsigned int)maxpages == 0)
3006                         maxpages = UINT_MAX;
3007         }
3008         p->highest_bit = maxpages - 1;
3009 
3010         if (!maxpages)
3011                 return 0;
3012         swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
3013         if (swapfilepages && maxpages > swapfilepages) {
3014                 pr_warn("Swap area shorter than signature indicates\n");
3015                 return 0;
3016         }
3017         if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
3018                 return 0;
3019         if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
3020                 return 0;
3021 
3022         return maxpages;
3023 }
3024 
3025 #define SWAP_CLUSTER_INFO_COLS                                          \
3026         DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
3027 #define SWAP_CLUSTER_SPACE_COLS                                         \
3028         DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
3029 #define SWAP_CLUSTER_COLS                                               \
3030         max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
3031 
3032 static int setup_swap_map_and_extents(struct swap_info_struct *p,
3033                                         union swap_header *swap_header,
3034                                         unsigned char *swap_map,
3035                                         struct swap_cluster_info *cluster_info,
3036                                         unsigned long maxpages,
3037                                         sector_t *span)
3038 {
3039         unsigned int j, k;
3040         unsigned int nr_good_pages;
3041         int nr_extents;
3042         unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3043         unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
3044         unsigned long i, idx;
3045 
3046         nr_good_pages = maxpages - 1;   /* omit header page */
3047 
3048         cluster_list_init(&p->free_clusters);
3049         cluster_list_init(&p->discard_clusters);
3050 
3051         for (i = 0; i < swap_header->info.nr_badpages; i++) {
3052                 unsigned int page_nr = swap_header->info.badpages[i];
3053                 if (page_nr == 0 || page_nr > swap_header->info.last_page)
3054                         return -EINVAL;
3055                 if (page_nr < maxpages) {
3056                         swap_map[page_nr] = SWAP_MAP_BAD;
3057                         nr_good_pages--;
3058                         /*
3059                          * Haven't marked the cluster free yet, no list
3060                          * operation involved
3061                          */
3062                         inc_cluster_info_page(p, cluster_info, page_nr);
3063                 }
3064         }
3065 
3066         /* Haven't marked the cluster free yet, no list operation involved */
3067         for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
3068                 inc_cluster_info_page(p, cluster_info, i);
3069 
3070         if (nr_good_pages) {
3071                 swap_map[0] = SWAP_MAP_BAD;
3072                 /*
3073                  * Not mark the cluster free yet, no list
3074                  * operation involved
3075                  */
3076                 inc_cluster_info_page(p, cluster_info, 0);
3077                 p->max = maxpages;
3078                 p->pages = nr_good_pages;
3079                 nr_extents = setup_swap_extents(p, span);
3080                 if (nr_extents < 0)
3081                         return nr_extents;
3082                 nr_good_pages = p->pages;
3083         }
3084         if (!nr_good_pages) {
3085                 pr_warn("Empty swap-file\n");
3086                 return -EINVAL;
3087         }
3088 
3089         if (!cluster_info)
3090                 return nr_extents;
3091 
3092 
3093         /*
3094          * Reduce false cache line sharing between cluster_info and
3095          * sharing same address space.
3096          */
3097         for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
3098                 j = (k + col) % SWAP_CLUSTER_COLS;
3099                 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
3100                         idx = i * SWAP_CLUSTER_COLS + j;
3101                         if (idx >= nr_clusters)
3102                                 continue;
3103                         if (cluster_count(&cluster_info[idx]))
3104                                 continue;
3105                         cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
3106                         cluster_list_add_tail(&p->free_clusters, cluster_info,
3107                                               idx);
3108                 }
3109         }
3110         return nr_extents;
3111 }
3112 
3113 /*
3114  * Helper to sys_swapon determining if a given swap
3115  * backing device queue supports DISCARD operations.
3116  */
3117 static bool swap_discardable(struct swap_info_struct *si)
3118 {
3119         struct request_queue *q = bdev_get_queue(si->bdev);
3120 
3121         if (!blk_queue_discard(q))
3122                 return false;
3123 
3124         return true;
3125 }
3126 
3127 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
3128 {
3129         struct swap_info_struct *p;
3130         struct filename *name;
3131         struct file *swap_file = NULL;
3132         struct address_space *mapping;
3133         struct dentry *dentry;
3134         int prio;
3135         int error;
3136         union swap_header *swap_header;
3137         int nr_extents;
3138         sector_t span;
3139         unsigned long maxpages;
3140         unsigned char *swap_map = NULL;
3141         struct swap_cluster_info *cluster_info = NULL;
3142         unsigned long *frontswap_map = NULL;
3143         struct page *page = NULL;
3144         struct inode *inode = NULL;
3145         bool inced_nr_rotate_swap = false;
3146 
3147         if (swap_flags & ~SWAP_FLAGS_VALID)
3148                 return -EINVAL;
3149 
3150         if (!capable(CAP_SYS_ADMIN))
3151                 return -EPERM;
3152 
3153         if (!swap_avail_heads)
3154                 return -ENOMEM;
3155 
3156         p = alloc_swap_info();
3157         if (IS_ERR(p))
3158                 return PTR_ERR(p);
3159 
3160         INIT_WORK(&p->discard_work, swap_discard_work);
3161 
3162         name = getname(specialfile);
3163         if (IS_ERR(name)) {
3164                 error = PTR_ERR(name);
3165                 name = NULL;
3166                 goto bad_swap;
3167         }
3168         swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
3169         if (IS_ERR(swap_file)) {
3170                 error = PTR_ERR(swap_file);
3171                 swap_file = NULL;
3172                 goto bad_swap;
3173         }
3174 
3175         p->swap_file = swap_file;
3176         mapping = swap_file->f_mapping;
3177         dentry = swap_file->f_path.dentry;
3178         inode = mapping->host;
3179 
3180         error = claim_swapfile(p, inode);
3181         if (unlikely(error))
3182                 goto bad_swap;
3183 
3184         inode_lock(inode);
3185         if (d_unlinked(dentry) || cant_mount(dentry)) {
3186                 error = -ENOENT;
3187                 goto bad_swap_unlock_inode;
3188         }
3189         if (IS_SWAPFILE(inode)) {
3190                 error = -EBUSY;
3191                 goto bad_swap_unlock_inode;
3192         }
3193 
3194         /*
3195          * Read the swap header.
3196          */
3197         if (!mapping->a_ops->readpage) {
3198                 error = -EINVAL;
3199                 goto bad_swap_unlock_inode;
3200         }
3201         page = read_mapping_page(mapping, 0, swap_file);
3202         if (IS_ERR(page)) {
3203                 error = PTR_ERR(page);
3204                 goto bad_swap_unlock_inode;
3205         }
3206         swap_header = kmap(page);
3207 
3208         maxpages = read_swap_header(p, swap_header, inode);
3209         if (unlikely(!maxpages)) {
3210                 error = -EINVAL;
3211                 goto bad_swap_unlock_inode;
3212         }
3213 
3214         /* OK, set up the swap map and apply the bad block list */
3215         swap_map = vzalloc(maxpages);
3216         if (!swap_map) {
3217                 error = -ENOMEM;
3218                 goto bad_swap_unlock_inode;
3219         }
3220 
3221         if (p->bdev && blk_queue_stable_writes(p->bdev->bd_disk->queue))
3222                 p->flags |= SWP_STABLE_WRITES;
3223 
3224         if (p->bdev && p->bdev->bd_disk->fops->rw_page)
3225                 p->flags |= SWP_SYNCHRONOUS_IO;
3226 
3227         if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
3228                 int cpu;
3229                 unsigned long ci, nr_cluster;
3230 
3231                 p->flags |= SWP_SOLIDSTATE;
3232                 p->cluster_next_cpu = alloc_percpu(unsigned int);
3233                 if (!p->cluster_next_cpu) {
3234                         error = -ENOMEM;
3235                         goto bad_swap_unlock_inode;
3236                 }
3237                 /*
3238                  * select a random position to start with to help wear leveling
3239                  * SSD
3240                  */
3241                 for_each_possible_cpu(cpu) {
3242                         per_cpu(*p->cluster_next_cpu, cpu) =
3243                                 1 + prandom_u32_max(p->highest_bit);
3244                 }
3245                 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
3246 
3247                 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
3248                                         GFP_KERNEL);
3249                 if (!cluster_info) {
3250                         error = -ENOMEM;
3251                         goto bad_swap_unlock_inode;
3252                 }
3253 
3254                 for (ci = 0; ci < nr_cluster; ci++)
3255                         spin_lock_init(&((cluster_info + ci)->lock));
3256 
3257                 p->percpu_cluster = alloc_percpu(struct percpu_cluster);
3258                 if (!p->percpu_cluster) {
3259                         error = -ENOMEM;
3260                         goto bad_swap_unlock_inode;
3261                 }
3262                 for_each_possible_cpu(cpu) {
3263                         struct percpu_cluster *cluster;
3264                         cluster = per_cpu_ptr(p->percpu_cluster, cpu);
3265                         cluster_set_null(&cluster->index);
3266                 }
3267         } else {
3268                 atomic_inc(&nr_rotate_swap);
3269                 inced_nr_rotate_swap = true;
3270         }
3271 
3272         error = swap_cgroup_swapon(p->type, maxpages);
3273         if (error)
3274                 goto bad_swap_unlock_inode;
3275 
3276         nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
3277                 cluster_info, maxpages, &span);
3278         if (unlikely(nr_extents < 0)) {
3279                 error = nr_extents;
3280                 goto bad_swap_unlock_inode;
3281         }
3282         /* frontswap enabled? set up bit-per-page map for frontswap */
3283         if (IS_ENABLED(CONFIG_FRONTSWAP))
3284                 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
3285                                          sizeof(long),
3286                                          GFP_KERNEL);
3287 
3288         if (p->bdev && (swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
3289                 /*
3290                  * When discard is enabled for swap with no particular
3291                  * policy flagged, we set all swap discard flags here in
3292                  * order to sustain backward compatibility with older
3293                  * swapon(8) releases.
3294                  */
3295                 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
3296                              SWP_PAGE_DISCARD);
3297 
3298                 /*
3299                  * By flagging sys_swapon, a sysadmin can tell us to
3300                  * either do single-time area discards only, or to just
3301                  * perform discards for released swap page-clusters.
3302                  * Now it's time to adjust the p->flags accordingly.
3303                  */
3304                 if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
3305                         p->flags &= ~SWP_PAGE_DISCARD;
3306                 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
3307                         p->flags &= ~SWP_AREA_DISCARD;
3308 
3309                 /* issue a swapon-time discard if it's still required */
3310                 if (p->flags & SWP_AREA_DISCARD) {
3311                         int err = discard_swap(p);
3312                         if (unlikely(err))
3313                                 pr_err("swapon: discard_swap(%p): %d\n",
3314                                         p, err);
3315                 }
3316         }
3317 
3318         error = init_swap_address_space(p->type, maxpages);
3319         if (error)
3320                 goto bad_swap_unlock_inode;
3321 
3322         /*
3323          * Flush any pending IO and dirty mappings before we start using this
3324          * swap device.
3325          */
3326         inode->i_flags |= S_SWAPFILE;
3327         error = inode_drain_writes(inode);
3328         if (error) {
3329                 inode->i_flags &= ~S_SWAPFILE;
3330                 goto free_swap_address_space;
3331         }
3332 
3333         mutex_lock(&swapon_mutex);
3334         prio = -1;
3335         if (swap_flags & SWAP_FLAG_PREFER)
3336                 prio =
3337                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
3338         enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
3339 
3340         pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
3341                 p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
3342                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
3343                 (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
3344                 (p->flags & SWP_DISCARDABLE) ? "D" : "",
3345                 (p->flags & SWP_AREA_DISCARD) ? "s" : "",
3346                 (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
3347                 (frontswap_map) ? "FS" : "");
3348 
3349         mutex_unlock(&swapon_mutex);
3350         atomic_inc(&proc_poll_event);
3351         wake_up_interruptible(&proc_poll_wait);
3352 
3353         error = 0;
3354         goto out;
3355 free_swap_address_space:
3356         exit_swap_address_space(p->type);
3357 bad_swap_unlock_inode:
3358         inode_unlock(inode);
3359 bad_swap:
3360         free_percpu(p->percpu_cluster);
3361         p->percpu_cluster = NULL;
3362         free_percpu(p->cluster_next_cpu);
3363         p->cluster_next_cpu = NULL;
3364         if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
3365                 set_blocksize(p->bdev, p->old_block_size);
3366                 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
3367         }
3368         inode = NULL;
3369         destroy_swap_extents(p);
3370         swap_cgroup_swapoff(p->type);
3371         spin_lock(&swap_lock);
3372         p->swap_file = NULL;
3373         p->flags = 0;
3374         spin_unlock(&swap_lock);
3375         vfree(swap_map);
3376         kvfree(cluster_info);
3377         kvfree(frontswap_map);
3378         if (inced_nr_rotate_swap)
3379                 atomic_dec(&nr_rotate_swap);
3380         if (swap_file)
3381                 filp_close(swap_file, NULL);
3382 out:
3383         if (page && !IS_ERR(page)) {
3384                 kunmap(page);
3385                 put_page(page);
3386         }
3387         if (name)
3388                 putname(name);
3389         if (inode)
3390                 inode_unlock(inode);
3391         if (!error)
3392                 enable_swap_slots_cache();
3393         return error;
3394 }
3395 
3396 void si_swapinfo(struct sysinfo *val)
3397 {
3398         unsigned int type;
3399         unsigned long nr_to_be_unused = 0;
3400 
3401         spin_lock(&swap_lock);
3402         for (type = 0; type < nr_swapfiles; type++) {
3403                 struct swap_info_struct *si = swap_info[type];
3404 
3405                 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
3406                         nr_to_be_unused += si->inuse_pages;
3407         }
3408         val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
3409         val->totalswap = total_swap_pages + nr_to_be_unused;
3410         spin_unlock(&swap_lock);
3411 }
3412 
3413 /*
3414  * Verify that a swap entry is valid and increment its swap map count.
3415  *
3416  * Returns error code in following case.
3417  * - success -> 0
3418  * - swp_entry is invalid -> EINVAL
3419  * - swp_entry is migration entry -> EINVAL
3420  * - swap-cache reference is requested but there is already one. -> EEXIST
3421  * - swap-cache reference is requested but the entry is not used. -> ENOENT
3422  * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
3423  */
3424 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
3425 {
3426         struct swap_info_struct *p;
3427         struct swap_cluster_info *ci;
3428         unsigned long offset;
3429         unsigned char count;
3430         unsigned char has_cache;
3431         int err;
3432 
3433         p = get_swap_device(entry);
3434         if (!p)
3435                 return -EINVAL;
3436 
3437         offset = swp_offset(entry);
3438         ci = lock_cluster_or_swap_info(p, offset);
3439 
3440         count = p->swap_map[offset];
3441 
3442         /*
3443          * swapin_readahead() doesn't check if a swap entry is valid, so the
3444          * swap entry could be SWAP_MAP_BAD. Check here with lock held.
3445          */
3446         if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
3447                 err = -ENOENT;
3448                 goto unlock_out;
3449         }
3450 
3451         has_cache = count & SWAP_HAS_CACHE;
3452         count &= ~SWAP_HAS_CACHE;
3453         err = 0;
3454 
3455         if (usage == SWAP_HAS_CACHE) {
3456 
3457                 /* set SWAP_HAS_CACHE if there is no cache and entry is used */
3458                 if (!has_cache && count)
3459                         has_cache = SWAP_HAS_CACHE;
3460                 else if (has_cache)             /* someone else added cache */
3461                         err = -EEXIST;
3462                 else                            /* no users remaining */
3463                         err = -ENOENT;
3464 
3465         } else if (count || has_cache) {
3466 
3467                 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
3468                         count += usage;
3469                 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
3470                         err = -EINVAL;
3471                 else if (swap_count_continued(p, offset, count))
3472                         count = COUNT_CONTINUED;
3473                 else
3474                         err = -ENOMEM;
3475         } else
3476                 err = -ENOENT;                  /* unused swap entry */
3477 
3478         WRITE_ONCE(p->swap_map[offset], count | has_cache);
3479 
3480 unlock_out:
3481         unlock_cluster_or_swap_info(p, ci);
3482         if (p)
3483                 put_swap_device(p);
3484         return err;
3485 }
3486 
3487 /*
3488  * Help swapoff by noting that swap entry belongs to shmem/tmpfs
3489  * (in which case its reference count is never incremented).
3490  */
3491 void swap_shmem_alloc(swp_entry_t entry)
3492 {
3493         __swap_duplicate(entry, SWAP_MAP_SHMEM);
3494 }
3495 
3496 /*
3497  * Increase reference count of swap entry by 1.
3498  * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
3499  * but could not be atomically allocated.  Returns 0, just as if it succeeded,
3500  * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
3501  * might occur if a page table entry has got corrupted.
3502  */
3503 int swap_duplicate(swp_entry_t entry)
3504 {
3505         int err = 0;
3506 
3507         while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
3508                 err = add_swap_count_continuation(entry, GFP_ATOMIC);
3509         return err;
3510 }
3511 
3512 /*
3513  * @entry: swap entry for which we allocate swap cache.
3514  *
3515  * Called when allocating swap cache for existing swap entry,
3516  * This can return error codes. Returns 0 at success.
3517  * -EEXIST means there is a swap cache.
3518  * Note: return code is different from swap_duplicate().
3519  */
3520 int swapcache_prepare(swp_entry_t entry)
3521 {
3522         return __swap_duplicate(entry, SWAP_HAS_CACHE);
3523 }
3524 
3525 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
3526 {
3527         return swap_type_to_swap_info(swp_type(entry));
3528 }
3529 
3530 struct swap_info_struct *page_swap_info(struct page *page)
3531 {
3532         swp_entry_t entry = { .val = page_private(page) };
3533         return swp_swap_info(entry);
3534 }
3535 
3536 /*
3537  * out-of-line methods to avoid include hell.
3538  */
3539 struct address_space *swapcache_mapping(struct folio *folio)
3540 {
3541         return page_swap_info(&folio->page)->swap_file->f_mapping;
3542 }
3543 EXPORT_SYMBOL_GPL(swapcache_mapping);
3544 
3545 pgoff_t __page_file_index(struct page *page)
3546 {
3547         swp_entry_t swap = { .val = page_private(page) };
3548         return swp_offset(swap);
3549 }
3550 EXPORT_SYMBOL_GPL(__page_file_index);
3551 
3552 /*
3553  * add_swap_count_continuation - called when a swap count is duplicated
3554  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
3555  * page of the original vmalloc'ed swap_map, to hold the continuation count
3556  * (for that entry and for its neighbouring PAGE_SIZE swap entries).  Called
3557  * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
3558  *
3559  * These continuation pages are seldom referenced: the common paths all work
3560  * on the original swap_map, only referring to a continuation page when the
3561  * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
3562  *
3563  * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
3564  * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
3565  * can be called after dropping locks.
3566  */
3567 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
3568 {
3569         struct swap_info_struct *si;
3570         struct swap_cluster_info *ci;
3571         struct page *head;
3572         struct page *page;
3573         struct page *list_page;
3574         pgoff_t offset;
3575         unsigned char count;
3576         int ret = 0;
3577 
3578         /*
3579          * When debugging, it's easier to use __GFP_ZERO here; but it's better
3580          * for latency not to zero a page while GFP_ATOMIC and holding locks.
3581          */
3582         page = alloc_page(gfp_mask | __GFP_HIGHMEM);
3583 
3584         si = get_swap_device(entry);
3585         if (!si) {
3586                 /*
3587                  * An acceptable race has occurred since the failing
3588                  * __swap_duplicate(): the swap device may be swapoff
3589                  */
3590                 goto outer;
3591         }
3592         spin_lock(&si->lock);
3593 
3594         offset = swp_offset(entry);
3595 
3596         ci = lock_cluster(si, offset);
3597 
3598         count = swap_count(si->swap_map[offset]);
3599 
3600         if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
3601                 /*
3602                  * The higher the swap count, the more likely it is that tasks
3603                  * will race to add swap count continuation: we need to avoid
3604                  * over-provisioning.
3605                  */
3606                 goto out;
3607         }
3608 
3609         if (!page) {
3610                 ret = -ENOMEM;
3611                 goto out;
3612         }
3613 
3614         /*
3615          * We are fortunate that although vmalloc_to_page uses pte_offset_map,
3616          * no architecture is using highmem pages for kernel page tables: so it
3617          * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
3618          */
3619         head = vmalloc_to_page(si->swap_map + offset);
3620         offset &= ~PAGE_MASK;
3621 
3622         spin_lock(&si->cont_lock);
3623         /*
3624          * Page allocation does not initialize the page's lru field,
3625          * but it does always reset its private field.
3626          */
3627         if (!page_private(head)) {
3628                 BUG_ON(count & COUNT_CONTINUED);
3629                 INIT_LIST_HEAD(&head->lru);
3630                 set_page_private(head, SWP_CONTINUED);
3631                 si->flags |= SWP_CONTINUED;
3632         }
3633 
3634         list_for_each_entry(list_page, &head->lru, lru) {
3635                 unsigned char *map;
3636 
3637                 /*
3638                  * If the previous map said no continuation, but we've found
3639                  * a continuation page, free our allocation and use this one.
3640                  */
3641                 if (!(count & COUNT_CONTINUED))
3642                         goto out_unlock_cont;
3643 
3644                 map = kmap_atomic(list_page) + offset;
3645                 count = *map;
3646                 kunmap_atomic(map);
3647 
3648                 /*
3649                  * If this continuation count now has some space in it,
3650                  * free our allocation and use this one.
3651                  */
3652                 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
3653                         goto out_unlock_cont;
3654         }
3655 
3656         list_add_tail(&page->lru, &head->lru);
3657         page = NULL;                    /* now it's attached, don't free it */
3658 out_unlock_cont:
3659         spin_unlock(&si->cont_lock);
3660 out:
3661         unlock_cluster(ci);
3662         spin_unlock(&si->lock);
3663         put_swap_device(si);
3664 outer:
3665         if (page)
3666                 __free_page(page);
3667         return ret;
3668 }
3669 
3670 /*
3671  * swap_count_continued - when the original swap_map count is incremented
3672  * from SWAP_MAP_MAX, check if there is already a continuation page to carry
3673  * into, carry if so, or else fail until a new continuation page is allocated;
3674  * when the original swap_map count is decremented from 0 with continuation,
3675  * borrow from the continuation and report whether it still holds more.
3676  * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
3677  * lock.
3678  */
3679 static bool swap_count_continued(struct swap_info_struct *si,
3680                                  pgoff_t offset, unsigned char count)
3681 {
3682         struct page *head;
3683         struct page *page;
3684         unsigned char *map;
3685         bool ret;
3686 
3687         head = vmalloc_to_page(si->swap_map + offset);
3688         if (page_private(head) != SWP_CONTINUED) {
3689                 BUG_ON(count & COUNT_CONTINUED);
3690                 return false;           /* need to add count continuation */
3691         }
3692 
3693         spin_lock(&si->cont_lock);
3694         offset &= ~PAGE_MASK;
3695         page = list_next_entry(head, lru);
3696         map = kmap_atomic(page) + offset;
3697 
3698         if (count == SWAP_MAP_MAX)      /* initial increment from swap_map */
3699                 goto init_map;          /* jump over SWAP_CONT_MAX checks */
3700 
3701         if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
3702                 /*
3703                  * Think of how you add 1 to 999
3704                  */
3705                 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
3706                         kunmap_atomic(map);
3707                         page = list_next_entry(page, lru);
3708                         BUG_ON(page == head);
3709                         map = kmap_atomic(page) + offset;
3710                 }
3711                 if (*map == SWAP_CONT_MAX) {
3712                         kunmap_atomic(map);
3713                         page = list_next_entry(page, lru);
3714                         if (page == head) {
3715                                 ret = false;    /* add count continuation */
3716                                 goto out;
3717                         }
3718                         map = kmap_atomic(page) + offset;
3719 init_map:               *map = 0;               /* we didn't zero the page */
3720                 }
3721                 *map += 1;
3722                 kunmap_atomic(map);
3723                 while ((page = list_prev_entry(page, lru)) != head) {
3724                         map = kmap_atomic(page) + offset;
3725                         *map = COUNT_CONTINUED;
3726                         kunmap_atomic(map);
3727                 }
3728                 ret = true;                     /* incremented */
3729 
3730         } else {                                /* decrementing */
3731                 /*
3732                  * Think of how you subtract 1 from 1000
3733                  */
3734                 BUG_ON(count != COUNT_CONTINUED);
3735                 while (*map == COUNT_CONTINUED) {
3736                         kunmap_atomic(map);
3737                         page = list_next_entry(page, lru);
3738                         BUG_ON(page == head);
3739                         map = kmap_atomic(page) + offset;
3740                 }
3741                 BUG_ON(*map == 0);
3742                 *map -= 1;
3743                 if (*map == 0)
3744                         count = 0;
3745                 kunmap_atomic(map);
3746                 while ((page = list_prev_entry(page, lru)) != head) {
3747                         map = kmap_atomic(page) + offset;
3748                         *map = SWAP_CONT_MAX | count;
3749                         count = COUNT_CONTINUED;
3750                         kunmap_atomic(map);
3751                 }
3752                 ret = count == COUNT_CONTINUED;
3753         }
3754 out:
3755         spin_unlock(&si->cont_lock);
3756         return ret;
3757 }
3758 
3759 /*
3760  * free_swap_count_continuations - swapoff free all the continuation pages
3761  * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
3762  */
3763 static void free_swap_count_continuations(struct swap_info_struct *si)
3764 {
3765         pgoff_t offset;
3766 
3767         for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
3768                 struct page *head;
3769                 head = vmalloc_to_page(si->swap_map + offset);
3770                 if (page_private(head)) {
3771                         struct page *page, *next;
3772 
3773                         list_for_each_entry_safe(page, next, &head->lru, lru) {
3774                                 list_del(&page->lru);
3775                                 __free_page(page);
3776                         }
3777                 }
3778         }
3779 }
3780 
3781 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
3782 void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
3783 {
3784         struct swap_info_struct *si, *next;
3785         int nid = page_to_nid(page);
3786 
3787         if (!(gfp_mask & __GFP_IO))
3788                 return;
3789 
3790         if (!blk_cgroup_congested())
3791                 return;
3792 
3793         /*
3794          * We've already scheduled a throttle, avoid taking the global swap
3795          * lock.
3796          */
3797         if (current->throttle_queue)
3798                 return;
3799 
3800         spin_lock(&swap_avail_lock);
3801         plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
3802                                   avail_lists[nid]) {
3803                 if (si->bdev) {
3804                         blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
3805                         break;
3806                 }
3807         }
3808         spin_unlock(&swap_avail_lock);
3809 }
3810 #endif
3811 
3812 static int __init swapfile_init(void)
3813 {
3814         int nid;
3815 
3816         swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
3817                                          GFP_KERNEL);
3818         if (!swap_avail_heads) {
3819                 pr_emerg("Not enough memory for swap heads, swap is disabled\n");
3820                 return -ENOMEM;
3821         }
3822 
3823         for_each_node(nid)
3824                 plist_head_init(&swap_avail_heads[nid]);
3825 
3826         return 0;
3827 }
3828 subsys_initcall(swapfile_init);
3829 

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